/*global self*/
/*jshint latedef: nofunc*/

/* Documentation: https://web-platform-tests.org/writing-tests/testharness-api.html
 * (../docs/_writing-tests/testharness-api.md) */

export default function (self) {
  const location = self.location;

  (function (global_scope) {
    // default timeout is 10 seconds, test can override if needed
    var settings = {
      output: true,
      harness_timeout: {
        normal: 10000,
        long: 60000,
      },
      test_timeout: null,
      message_events: ["start", "test_state", "result", "completion"],
      debug: false,
    };

    var xhtml_ns = "http://www.w3.org/1999/xhtml";

    /*
     * TestEnvironment is an abstraction for the environment in which the test
     * harness is used. Each implementation of a test environment has to provide
     * the following interface:
     *
     * interface TestEnvironment {
     *   // Invoked after the global 'tests' object has been created and it's
     *   // safe to call add_*_callback() to register event handlers.
     *   void on_tests_ready();
     *
     *   // Invoked after setup() has been called to notify the test environment
     *   // of changes to the test harness properties.
     *   void on_new_harness_properties(object properties);
     *
     *   // Should return a new unique default test name.
     *   DOMString next_default_test_name();
     *
     *   // Should return the test harness timeout duration in milliseconds.
     *   float test_timeout();
     * };
     */

    /*
     * A test environment with a DOM. The global object is 'window'. By default
     * test results are displayed in a table. Any parent windows receive
     * callbacks or messages via postMessage() when test events occur. See
     * apisample11.html and apisample12.html.
     */
    function WindowTestEnvironment() {
      this.name_counter = 0;
      this.window_cache = null;
      this.output_handler = null;
      this.all_loaded = false;
      var this_obj = this;
      this.message_events = [];
      this.dispatched_messages = [];

      this.message_functions = {
        start: [
          add_start_callback,
          remove_start_callback,
          function (properties) {
            this_obj._dispatch("start_callback", [properties], {
              type: "start",
              properties: properties,
            });
          },
        ],

        test_state: [
          add_test_state_callback,
          remove_test_state_callback,
          function (test) {
            this_obj._dispatch("test_state_callback", [test], {
              type: "test_state",
              test: test.structured_clone(),
            });
          },
        ],
        result: [
          add_result_callback,
          remove_result_callback,
          function (test) {
            this_obj.output_handler.show_status();
            this_obj._dispatch("result_callback", [test], {
              type: "result",
              test: test.structured_clone(),
            });
          },
        ],
        completion: [
          add_completion_callback,
          remove_completion_callback,
          function (tests, harness_status, asserts) {
            var cloned_tests = map(tests, function (test) {
              return test.structured_clone();
            });
            this_obj._dispatch("completion_callback", [tests, harness_status], {
              type: "complete",
              tests: cloned_tests,
              status: harness_status.structured_clone(),
              asserts: asserts.map((assert) => assert.structured_clone()),
            });
          },
        ],
      };

      on_event(window, "load", function () {
        setTimeout(() => {
          this_obj.all_loaded = true;
          if (tests.all_done()) {
            tests.complete();
          }
        }, 0);
      });

      on_event(window, "message", function (event) {
        if (event.data && event.data.type === "getmessages" && event.source) {
          // A window can post "getmessages" to receive a duplicate of every
          // message posted by this environment so far. This allows subscribers
          // from fetch_tests_from_window to 'catch up' to the current state of
          // this environment.
          for (var i = 0; i < this_obj.dispatched_messages.length; ++i) {
            event.source.postMessage(this_obj.dispatched_messages[i], "*");
          }
        }
      });
    }

    WindowTestEnvironment.prototype._dispatch = function (
      selector,
      callback_args,
      message_arg
    ) {
      this.dispatched_messages.push(message_arg);
      this._forEach_windows(function (w, same_origin) {
        if (same_origin) {
          try {
            var has_selector = selector in w;
          } catch (e) {
            // If document.domain was set at some point same_origin can be
            // wrong and the above will fail.
            has_selector = false;
          }
          if (has_selector) {
            try {
              w[selector].apply(undefined, callback_args);
            } catch (e) {}
          }
        }
        if (w !== self) {
          w.postMessage(message_arg, "*");
        }
      });
    };

    WindowTestEnvironment.prototype._forEach_windows = function (callback) {
      // Iterate over the windows [self ... top, opener]. The callback is passed
      // two objects, the first one is the window object itself, the second one
      // is a boolean indicating whether or not it's on the same origin as the
      // current window.
      var cache = this.window_cache;
      if (!cache) {
        cache = [[self, true]];
        var w = self;
        var i = 0;
        var so;
        while (w != w.parent) {
          w = w.parent;
          so = is_same_origin(w);
          cache.push([w, so]);
          i++;
        }
        w = window.opener;
        if (w) {
          cache.push([w, is_same_origin(w)]);
        }
        this.window_cache = cache;
      }

      forEach(cache, function (a) {
        callback.apply(null, a);
      });
    };

    WindowTestEnvironment.prototype.on_tests_ready = function () {
      var output = new Output();
      this.output_handler = output;

      var this_obj = this;

      add_start_callback(function (properties) {
        this_obj.output_handler.init(properties);
      });

      add_test_state_callback(function (test) {
        this_obj.output_handler.show_status();
      });

      add_result_callback(function (test) {
        this_obj.output_handler.show_status();
      });

      add_completion_callback(function (tests, harness_status, asserts_run) {
        this_obj.output_handler.show_results(
          tests,
          harness_status,
          asserts_run
        );
      });
      this.setup_messages(settings.message_events);
    };

    WindowTestEnvironment.prototype.setup_messages = function (new_events) {
      var this_obj = this;
      forEach(settings.message_events, function (x) {
        var current_dispatch = this_obj.message_events.indexOf(x) !== -1;
        var new_dispatch = new_events.indexOf(x) !== -1;
        if (!current_dispatch && new_dispatch) {
          this_obj.message_functions[x][0](this_obj.message_functions[x][2]);
        } else if (current_dispatch && !new_dispatch) {
          this_obj.message_functions[x][1](this_obj.message_functions[x][2]);
        }
      });
      this.message_events = new_events;
    };

    WindowTestEnvironment.prototype.next_default_test_name = function () {
      var suffix = this.name_counter > 0 ? " " + this.name_counter : "";
      this.name_counter++;
      return get_title() + suffix;
    };

    WindowTestEnvironment.prototype.on_new_harness_properties = function (
      properties
    ) {
      this.output_handler.setup(properties);
      if (properties.hasOwnProperty("message_events")) {
        this.setup_messages(properties.message_events);
      }
    };

    WindowTestEnvironment.prototype.add_on_loaded_callback = function (
      callback
    ) {
      on_event(window, "load", callback);
    };

    WindowTestEnvironment.prototype.test_timeout = function () {
      var metas = document.getElementsByTagName("meta");
      for (var i = 0; i < metas.length; i++) {
        if (metas[i].name == "timeout") {
          if (metas[i].content == "long") {
            return settings.harness_timeout.long;
          }
          break;
        }
      }
      return settings.harness_timeout.normal;
    };

    /*
     * Base TestEnvironment implementation for a generic web worker.
     *
     * Workers accumulate test results. One or more clients can connect and
     * retrieve results from a worker at any time.
     *
     * WorkerTestEnvironment supports communicating with a client via a
     * MessagePort.  The mechanism for determining the appropriate MessagePort
     * for communicating with a client depends on the type of worker and is
     * implemented by the various specializations of WorkerTestEnvironment
     * below.
     *
     * A client document using testharness can use fetch_tests_from_worker() to
     * retrieve results from a worker. See apisample16.html.
     */
    function WorkerTestEnvironment() {
      this.name_counter = 0;
      this.all_loaded = true;
      this.message_list = [];
      this.message_ports = [];
    }

    WorkerTestEnvironment.prototype._dispatch = function (message) {
      this.message_list.push(message);
      for (var i = 0; i < this.message_ports.length; ++i) {
        this.message_ports[i].postMessage(message);
      }
    };

    // The only requirement is that port has a postMessage() method. It doesn't
    // have to be an instance of a MessagePort, and often isn't.
    WorkerTestEnvironment.prototype._add_message_port = function (port) {
      this.message_ports.push(port);
      for (var i = 0; i < this.message_list.length; ++i) {
        port.postMessage(this.message_list[i]);
      }
    };

    WorkerTestEnvironment.prototype.next_default_test_name = function () {
      var suffix = this.name_counter > 0 ? " " + this.name_counter : "";
      this.name_counter++;
      return get_title() + suffix;
    };

    WorkerTestEnvironment.prototype.on_new_harness_properties = function () {};

    WorkerTestEnvironment.prototype.on_tests_ready = function () {
      var this_obj = this;
      add_start_callback(function (properties) {
        this_obj._dispatch({
          type: "start",
          properties: properties,
        });
      });
      add_test_state_callback(function (test) {
        this_obj._dispatch({
          type: "test_state",
          test: test.structured_clone(),
        });
      });
      add_result_callback(function (test) {
        this_obj._dispatch({
          type: "result",
          test: test.structured_clone(),
        });
      });
      add_completion_callback(function (tests, harness_status, asserts) {
        this_obj._dispatch({
          type: "complete",
          tests: map(tests, function (test) {
            return test.structured_clone();
          }),
          status: harness_status.structured_clone(),
          asserts: asserts.map((assert) => assert.structured_clone()),
        });
      });
    };

    WorkerTestEnvironment.prototype.add_on_loaded_callback = function () {};

    WorkerTestEnvironment.prototype.test_timeout = function () {
      // Tests running in a worker don't have a default timeout. I.e. all
      // worker tests behave as if settings.explicit_timeout is true.
      return null;
    };

    /*
     * Dedicated web workers.
     * https://html.spec.whatwg.org/multipage/workers.html#dedicatedworkerglobalscope
     *
     * This class is used as the test_environment when testharness is running
     * inside a dedicated worker.
     */
    function DedicatedWorkerTestEnvironment() {
      WorkerTestEnvironment.call(this);
      // self is an instance of DedicatedWorkerGlobalScope which exposes
      // a postMessage() method for communicating via the message channel
      // established when the worker is created.
      this._add_message_port(self);
    }
    DedicatedWorkerTestEnvironment.prototype = Object.create(
      WorkerTestEnvironment.prototype
    );

    DedicatedWorkerTestEnvironment.prototype.on_tests_ready = function () {
      WorkerTestEnvironment.prototype.on_tests_ready.call(this);
      // In the absence of an onload notification, we a require dedicated
      // workers to explicitly signal when the tests are done.
      tests.wait_for_finish = true;
    };

    /*
     * Shared web workers.
     * https://html.spec.whatwg.org/multipage/workers.html#sharedworkerglobalscope
     *
     * This class is used as the test_environment when testharness is running
     * inside a shared web worker.
     */
    function SharedWorkerTestEnvironment() {
      WorkerTestEnvironment.call(this);
      var this_obj = this;
      // Shared workers receive message ports via the 'onconnect' event for
      // each connection.
      self.addEventListener(
        "connect",
        function (message_event) {
          this_obj._add_message_port(message_event.source);
        },
        false
      );
    }
    SharedWorkerTestEnvironment.prototype = Object.create(
      WorkerTestEnvironment.prototype
    );

    SharedWorkerTestEnvironment.prototype.on_tests_ready = function () {
      WorkerTestEnvironment.prototype.on_tests_ready.call(this);
      // In the absence of an onload notification, we a require shared
      // workers to explicitly signal when the tests are done.
      tests.wait_for_finish = true;
    };

    /*
     * Service workers.
     * http://www.w3.org/TR/service-workers/
     *
     * This class is used as the test_environment when testharness is running
     * inside a service worker.
     */
    function ServiceWorkerTestEnvironment() {
      WorkerTestEnvironment.call(this);
      this.all_loaded = false;
      this.on_loaded_callback = null;
      var this_obj = this;
      self.addEventListener(
        "message",
        function (event) {
          if (event.data && event.data.type && event.data.type === "connect") {
            this_obj._add_message_port(event.source);
          }
        },
        false
      );

      // The oninstall event is received after the service worker script and
      // all imported scripts have been fetched and executed. It's the
      // equivalent of an onload event for a document. All tests should have
      // been added by the time this event is received, thus it's not
      // necessary to wait until the onactivate event. However, tests for
      // installed service workers need another event which is equivalent to
      // the onload event because oninstall is fired only on installation. The
      // onmessage event is used for that purpose since tests using
      // testharness.js should ask the result to its service worker by
      // PostMessage. If the onmessage event is triggered on the service
      // worker's context, that means the worker's script has been evaluated.
      on_event(self, "install", on_all_loaded);
      on_event(self, "message", on_all_loaded);
      function on_all_loaded() {
        if (this_obj.all_loaded) return;
        this_obj.all_loaded = true;
        if (this_obj.on_loaded_callback) {
          this_obj.on_loaded_callback();
        }
      }
    }

    ServiceWorkerTestEnvironment.prototype = Object.create(
      WorkerTestEnvironment.prototype
    );

    ServiceWorkerTestEnvironment.prototype.add_on_loaded_callback = function (
      callback
    ) {
      if (this.all_loaded) {
        callback();
      } else {
        this.on_loaded_callback = callback;
      }
    };

    /*
     * Shadow realms.
     * https://github.com/tc39/proposal-shadowrealm
     *
     * This class is used as the test_environment when testharness is running
     * inside a shadow realm.
     */
    function ShadowRealmTestEnvironment() {
      WorkerTestEnvironment.call(this);
      this.all_loaded = false;
      this.on_loaded_callback = null;
    }

    ShadowRealmTestEnvironment.prototype = Object.create(
      WorkerTestEnvironment.prototype
    );

    /**
     * Signal to the test environment that the tests are ready and the on-loaded
     * callback should be run.
     *
     * Shadow realms are not *really* a DOM context: they have no `onload` or similar
     * event for us to use to set up the test environment; so, instead, this method
     * is manually triggered from the incubating realm
     *
     * @param {Function} message_destination - a function that receives JSON-serializable
     * data to send to the incubating realm, in the same format as used by RemoteContext
     */
    ShadowRealmTestEnvironment.prototype.begin = function (
      message_destination
    ) {
      if (this.all_loaded) {
        throw new Error(
          "Tried to start a shadow realm test environment after it has already started"
        );
      }
      var fakeMessagePort = {};
      fakeMessagePort.postMessage = message_destination;
      this._add_message_port(fakeMessagePort);
      this.all_loaded = true;
      if (this.on_loaded_callback) {
        this.on_loaded_callback();
      }
    };

    ShadowRealmTestEnvironment.prototype.add_on_loaded_callback = function (
      callback
    ) {
      if (this.all_loaded) {
        callback();
      } else {
        this.on_loaded_callback = callback;
      }
    };

    /*
     * JavaScript shells.
     *
     * This class is used as the test_environment when testharness is running
     * inside a JavaScript shell.
     */
    function ShellTestEnvironment() {
      this.name_counter = 0;
      this.all_loaded = false;
      this.on_loaded_callback = null;
      Promise.resolve().then(
        function () {
          this.all_loaded = true;
          if (this.on_loaded_callback) {
            this.on_loaded_callback();
          }
        }.bind(this)
      );
      this.message_list = [];
      this.message_ports = [];
    }

    ShellTestEnvironment.prototype.next_default_test_name = function () {
      var suffix = this.name_counter > 0 ? " " + this.name_counter : "";
      this.name_counter++;
      return get_title() + suffix;
    };

    ShellTestEnvironment.prototype.on_new_harness_properties = function () {};

    ShellTestEnvironment.prototype.on_tests_ready = function () {};

    ShellTestEnvironment.prototype.add_on_loaded_callback = function (
      callback
    ) {
      if (this.all_loaded) {
        callback();
      } else {
        this.on_loaded_callback = callback;
      }
    };

    ShellTestEnvironment.prototype.test_timeout = function () {
      // Tests running in a shell don't have a default timeout, so behave as
      // if settings.explicit_timeout is true.
      return null;
    };

    function create_test_environment() {
      if ("document" in global_scope) {
        return new WindowTestEnvironment();
      }
      if (
        "DedicatedWorkerGlobalScope" in global_scope &&
        global_scope instanceof DedicatedWorkerGlobalScope
      ) {
        return new DedicatedWorkerTestEnvironment();
      }
      if (
        "SharedWorkerGlobalScope" in global_scope &&
        global_scope instanceof SharedWorkerGlobalScope
      ) {
        return new SharedWorkerTestEnvironment();
      }
      if (
        "ServiceWorkerGlobalScope" in global_scope &&
        global_scope instanceof ServiceWorkerGlobalScope
      ) {
        return new ServiceWorkerTestEnvironment();
      }
      if (
        "WorkerGlobalScope" in global_scope &&
        global_scope instanceof WorkerGlobalScope
      ) {
        return new DedicatedWorkerTestEnvironment();
      }
      /* Shadow realm global objects are _ordinary_ objects (i.e. their prototype is
       * Object) so we don't have a nice `instanceof` test to use; instead, we
       * check if the there is a GLOBAL.isShadowRealm() property
       * on the global object. that was set by the test harness when it
       * created the ShadowRealm.
       */
      if (global_scope.GLOBAL && global_scope.GLOBAL.isShadowRealm()) {
        return new ShadowRealmTestEnvironment();
      }

      return new ShellTestEnvironment();
    }

    var test_environment = create_test_environment();

    function is_shared_worker(worker) {
      return "SharedWorker" in global_scope && worker instanceof SharedWorker;
    }

    function is_service_worker(worker) {
      // The worker object may be from another execution context,
      // so do not use instanceof here.
      return (
        "ServiceWorker" in global_scope &&
        Object.prototype.toString.call(worker) == "[object ServiceWorker]"
      );
    }

    var seen_func_name = Object.create(null);

    function get_test_name(func, name) {
      if (name) {
        return name;
      }

      if (func) {
        var func_code = func.toString();

        // Try and match with brackets, but fallback to matching without
        var arrow = func_code.match(/^\(\)\s*=>\s*(?:{(.*)}\s*|(.*))$/);

        // Check for JS line separators
        if (arrow !== null && !/[\u000A\u000D\u2028\u2029]/.test(func_code)) {
          var trimmed = (arrow[1] !== undefined ? arrow[1] : arrow[2]).trim();
          // drop trailing ; if there's no earlier ones
          trimmed = trimmed.replace(/^([^;]*)(;\s*)+$/, "$1");

          if (trimmed) {
            let name = trimmed;
            if (seen_func_name[trimmed]) {
              // This subtest name already exists, so add a suffix.
              name += " " + seen_func_name[trimmed];
            } else {
              seen_func_name[trimmed] = 0;
            }
            seen_func_name[trimmed] += 1;
            return name;
          }
        }
      }

      return test_environment.next_default_test_name();
    }

    /**
     * @callback TestFunction
     * @param {Test} test - The test currnetly being run.
     * @param {Any[]} args - Additional args to pass to function.
     *
     */

    /**
     * Create a synchronous test
     *
     * @param {TestFunction} func - Test function. This is executed
     * immediately. If it returns without error, the test status is
     * set to ``PASS``. If it throws an :js:class:`AssertionError`, or
     * any other exception, the test status is set to ``FAIL``
     * (typically from an `assert` function).
     * @param {String} name - Test name. This must be unique in a
     * given file and must be invariant between runs.
     */
    function test(func, name, properties) {
      if (tests.promise_setup_called) {
        tests.status.status = tests.status.ERROR;
        tests.status.message = "`test` invoked after `promise_setup`";
        tests.complete();
      }
      var test_name = get_test_name(func, name);
      var test_obj = new Test(test_name, properties);
      var value = test_obj.step(func, test_obj, test_obj);

      if (value !== undefined) {
        var msg =
          'Test named "' +
          test_name +
          '" passed a function to `test` that returned a value.';

        try {
          if (value && typeof value.then === "function") {
            msg +=
              " Consider using `promise_test` instead when " +
              "using Promises or async/await.";
          }
        } catch (err) {}

        tests.status.status = tests.status.ERROR;
        tests.status.message = msg;
      }

      if (test_obj.phase === test_obj.phases.STARTED) {
        test_obj.done();
      }
    }

    /**
     * Create an asynchronous test
     *
     * @param {TestFunction|string} funcOrName - Initial step function
     * to call immediately with the test name as an argument (if any),
     * or name of the test.
     * @param {String} name - Test name (if a test function was
     * provided). This must be unique in a given file and must be
     * invariant between runs.
     * @returns {Test} An object representing the ongoing test.
     */
    function async_test(func, name, properties) {
      if (tests.promise_setup_called) {
        tests.status.status = tests.status.ERROR;
        tests.status.message = "`async_test` invoked after `promise_setup`";
        tests.complete();
      }
      if (typeof func !== "function") {
        properties = name;
        name = func;
        func = null;
      }
      var test_name = get_test_name(func, name);
      var test_obj = new Test(test_name, properties);
      if (func) {
        var value = test_obj.step(func, test_obj, test_obj);

        // Test authors sometimes return values to async_test, expecting us
        // to handle the value somehow. Make doing so a harness error to be
        // clear this is invalid, and point authors to promise_test if it
        // may be appropriate.
        //
        // Note that we only perform this check on the initial function
        // passed to async_test, not on any later steps - we haven't seen a
        // consistent problem with those (and it's harder to check).
        if (value !== undefined) {
          var msg =
            'Test named "' +
            test_name +
            '" passed a function to `async_test` that returned a value.';

          try {
            if (value && typeof value.then === "function") {
              msg +=
                " Consider using `promise_test` instead when " +
                "using Promises or async/await.";
            }
          } catch (err) {}

          tests.set_status(tests.status.ERROR, msg);
          tests.complete();
        }
      }
      return test_obj;
    }

    /**
     * Create a promise test.
     *
     * Promise tests are tests which are represented by a promise
     * object. If the promise is fulfilled the test passes, if it's
     * rejected the test fails, otherwise the test passes.
     *
     * @param {TestFunction} func - Test function. This must return a
     * promise. The test is automatically marked as complete once the
     * promise settles.
     * @param {String} name - Test name. This must be unique in a
     * given file and must be invariant between runs.
     */
    function promise_test(func, name, properties) {
      if (typeof func !== "function") {
        properties = name;
        name = func;
        func = null;
      }
      var test_name = get_test_name(func, name);
      var test = new Test(test_name, properties);
      test._is_promise_test = true;

      // If there is no promise tests queue make one.
      if (!tests.promise_tests) {
        tests.promise_tests = Promise.resolve();
      }
      tests.promise_tests = tests.promise_tests.then(function () {
        return new Promise(function (resolve) {
          var promise = test.step(func, test, test);

          test.step(function () {
            assert(
              !!promise,
              "promise_test",
              null,
              "test body must return a 'thenable' object (received ${value})",
              { value: promise }
            );
            assert(
              typeof promise.then === "function",
              "promise_test",
              null,
              "test body must return a 'thenable' object (received an object with no `then` method)",
              null
            );
          });

          // Test authors may use the `step` method within a
          // `promise_test` even though this reflects a mixture of
          // asynchronous control flow paradigms. The "done" callback
          // should be registered prior to the resolution of the
          // user-provided Promise to avoid timeouts in cases where the
          // Promise does not settle but a `step` function has thrown an
          // error.
          add_test_done_callback(test, resolve);

          Promise.resolve(promise)
            .catch(
              test.step_func(function (value) {
                if (value instanceof AssertionError) {
                  throw value;
                }
                assert(
                  false,
                  "promise_test",
                  null,
                  "Unhandled rejection with value: ${value}",
                  { value: value }
                );
              })
            )
            .then(function () {
              test.done();
            });
        });
      });
    }

    /**
     * Make a copy of a Promise in the current realm.
     *
     * @param {Promise} promise the given promise that may be from a different
     *                          realm
     * @returns {Promise}
     *
     * An arbitrary promise provided by the caller may have originated
     * in another frame that have since navigated away, rendering the
     * frame's document inactive. Such a promise cannot be used with
     * `await` or Promise.resolve(), as microtasks associated with it
     * may be prevented from being run. See `issue
     * 5319<https://github.com/whatwg/html/issues/5319>`_ for a
     * particular case.
     *
     * In functions we define here, there is an expectation from the caller
     * that the promise is from the current realm, that can always be used with
     * `await`, etc. We therefore create a new promise in this realm that
     * inherit the value and status from the given promise.
     */

    function bring_promise_to_current_realm(promise) {
      return new Promise(promise.then.bind(promise));
    }

    /**
     * Assert that a Promise is rejected with the right ECMAScript exception.
     *
     * @param {Test} test - the `Test` to use for the assertion.
     * @param {Function} constructor - The expected exception constructor.
     * @param {Promise} promise - The promise that's expected to
     * reject with the given exception.
     * @param {string} [description] Error message to add to assert in case of
     *                               failure.
     */
    function promise_rejects_js(test, constructor, promise, description) {
      return bring_promise_to_current_realm(promise)
        .then(test.unreached_func("Should have rejected: " + description))
        .catch(function (e) {
          assert_throws_js_impl(
            constructor,
            function () {
              throw e;
            },
            description,
            "promise_rejects_js"
          );
        });
    }

    /**
     * Assert that a Promise is rejected with the right DOMException.
     *
     * For the remaining arguments, there are two ways of calling
     * promise_rejects_dom:
     *
     * 1) If the DOMException is expected to come from the current global, the
     * third argument should be the promise expected to reject, and a fourth,
     * optional, argument is the assertion description.
     *
     * 2) If the DOMException is expected to come from some other global, the
     * third argument should be the DOMException constructor from that global,
     * the fourth argument the promise expected to reject, and the fifth,
     * optional, argument the assertion description.
     *
     * @param {Test} test - the `Test` to use for the assertion.
     * @param {number|string} type - See documentation for
     * `assert_throws_dom <#assert_throws_dom>`_.
     * @param {Function} promiseOrConstructor - Either the constructor
     * for the expected exception (if the exception comes from another
     * global), or the promise that's expected to reject (if the
     * exception comes from the current global).
     * @param {Function|string} descriptionOrPromise - Either the
     * promise that's expected to reject (if the exception comes from
     * another global), or the optional description of the condition
     * being tested (if the exception comes from the current global).
     * @param {string} [description] - Description of the condition
     * being tested (if the exception comes from another global).
     *
     */
    function promise_rejects_dom(
      test,
      type,
      promiseOrConstructor,
      descriptionOrPromise,
      maybeDescription
    ) {
      let constructor, promise, description;
      if (
        typeof promiseOrConstructor === "function" &&
        promiseOrConstructor.name === "DOMException"
      ) {
        constructor = promiseOrConstructor;
        promise = descriptionOrPromise;
        description = maybeDescription;
      } else {
        constructor = self.DOMException;
        promise = promiseOrConstructor;
        description = descriptionOrPromise;
        assert(
          maybeDescription === undefined,
          "Too many args passed to no-constructor version of promise_rejects_dom, or accidentally explicitly passed undefined"
        );
      }
      return bring_promise_to_current_realm(promise)
        .then(test.unreached_func("Should have rejected: " + description))
        .catch(function (e) {
          assert_throws_dom_impl(
            type,
            function () {
              throw e;
            },
            description,
            "promise_rejects_dom",
            constructor
          );
        });
    }

    /**
     * Assert that a Promise is rejected with the provided value.
     *
     * @param {Test} test - the `Test` to use for the assertion.
     * @param {Any} exception - The expected value of the rejected promise.
     * @param {Promise} promise - The promise that's expected to
     * reject.
     * @param {string} [description] Error message to add to assert in case of
     *                               failure.
     */
    function promise_rejects_exactly(test, exception, promise, description) {
      return bring_promise_to_current_realm(promise)
        .then(test.unreached_func("Should have rejected: " + description))
        .catch(function (e) {
          assert_throws_exactly_impl(
            exception,
            function () {
              throw e;
            },
            description,
            "promise_rejects_exactly"
          );
        });
    }

    /**
     * Allow DOM events to be handled using Promises.
     *
     * This can make it a lot easier to test a very specific series of events,
     * including ensuring that unexpected events are not fired at any point.
     *
     * `EventWatcher` will assert if an event occurs while there is no `wait_for`
     * created Promise waiting to be fulfilled, or if the event is of a different type
     * to the type currently expected. This ensures that only the events that are
     * expected occur, in the correct order, and with the correct timing.
     *
     * @constructor
     * @param {Test} test - The `Test` to use for the assertion.
     * @param {EventTarget} watchedNode - The target expected to receive the events.
     * @param {string[]} eventTypes - List of events to watch for.
     * @param {Promise} timeoutPromise - Promise that will cause the
     * test to be set to `TIMEOUT` once fulfilled.
     *
     */
    function EventWatcher(test, watchedNode, eventTypes, timeoutPromise) {
      if (typeof eventTypes == "string") {
        eventTypes = [eventTypes];
      }

      var waitingFor = null;

      // This is null unless we are recording all events, in which case it
      // will be an Array object.
      var recordedEvents = null;

      var eventHandler = test.step_func(function (evt) {
        assert_true(
          !!waitingFor,
          "Not expecting event, but got " + evt.type + " event"
        );
        assert_equals(
          evt.type,
          waitingFor.types[0],
          "Expected " +
            waitingFor.types[0] +
            " event, but got " +
            evt.type +
            " event instead"
        );

        if (Array.isArray(recordedEvents)) {
          recordedEvents.push(evt);
        }

        if (waitingFor.types.length > 1) {
          // Pop first event from array
          waitingFor.types.shift();
          return;
        }
        // We need to null out waitingFor before calling the resolve function
        // since the Promise's resolve handlers may call wait_for() which will
        // need to set waitingFor.
        var resolveFunc = waitingFor.resolve;
        waitingFor = null;
        // Likewise, we should reset the state of recordedEvents.
        var result = recordedEvents || evt;
        recordedEvents = null;
        resolveFunc(result);
      });

      for (var i = 0; i < eventTypes.length; i++) {
        watchedNode.addEventListener(eventTypes[i], eventHandler, false);
      }

      /**
       * Returns a Promise that will resolve after the specified event or
       * series of events has occurred.
       *
       * @param {Object} options An optional options object. If the 'record' property
       *                 on this object has the value 'all', when the Promise
       *                 returned by this function is resolved,  *all* Event
       *                 objects that were waited for will be returned as an
       *                 array.
       *
       * @example
       * const watcher = new EventWatcher(t, div, [ 'animationstart',
       *                                            'animationiteration',
       *                                            'animationend' ]);
       * return watcher.wait_for([ 'animationstart', 'animationend' ],
       *                         { record: 'all' }).then(evts => {
       *   assert_equals(evts[0].elapsedTime, 0.0);
       *   assert_equals(evts[1].elapsedTime, 2.0);
       * });
       */
      this.wait_for = function (types, options) {
        if (waitingFor) {
          return Promise.reject("Already waiting for an event or events");
        }
        if (typeof types == "string") {
          types = [types];
        }
        if (options && options.record && options.record === "all") {
          recordedEvents = [];
        }
        return new Promise(function (resolve, reject) {
          var timeout = test.step_func(function () {
            // If the timeout fires after the events have been received
            // or during a subsequent call to wait_for, ignore it.
            if (!waitingFor || waitingFor.resolve !== resolve) return;

            // This should always fail, otherwise we should have
            // resolved the promise.
            assert_true(
              waitingFor.types.length == 0,
              "Timed out waiting for " + waitingFor.types.join(", ")
            );
            var result = recordedEvents;
            recordedEvents = null;
            var resolveFunc = waitingFor.resolve;
            waitingFor = null;
            resolveFunc(result);
          });

          if (timeoutPromise) {
            timeoutPromise().then(timeout);
          }

          waitingFor = {
            types: types,
            resolve: resolve,
            reject: reject,
          };
        });
      };

      /**
       * Stop listening for events
       */
      function stop_watching() {
        for (var i = 0; i < eventTypes.length; i++) {
          watchedNode.removeEventListener(eventTypes[i], eventHandler, false);
        }
      }

      test._add_cleanup(stop_watching);

      return this;
    }
    expose(EventWatcher, "EventWatcher");

    /**
     * @typedef {Object} SettingsObject
     * @property {bool} single_test - Use the single-page-test
     * mode. In this mode the Document represents a single
     * `async_test`. Asserts may be used directly without requiring
     * `Test.step` or similar wrappers, and any exceptions set the
     * status of the test rather than the status of the harness.
     * @property {bool} allow_uncaught_exception - don't treat an
     * uncaught exception as an error; needed when e.g. testing the
     * `window.onerror` handler.
     * @property {boolean} explicit_done - Wait for a call to `done()`
     * before declaring all tests complete (this is always true for
     * single-page tests).
     * @property hide_test_state - hide the test state output while
     * the test is running; This is helpful when the output of the test state
     * may interfere the test results.
     * @property {bool} explicit_timeout - disable file timeout; only
     * stop waiting for results when the `timeout()` function is
     * called This should typically only be set for manual tests, or
     * by a test runner that providees its own timeout mechanism.
     * @property {number} timeout_multiplier - Multiplier to apply to
     * per-test timeouts. This should only be set by a test runner.
     * @property {Document} output_document - The document to which
     * results should be logged. By default this is the current
     * document but could be an ancestor document in some cases e.g. a
     * SVG test loaded in an HTML wrapper
     *
     */

    /**
     * Configure the harness
     *
     * @param {Function|SettingsObject} funcOrProperties - Either a
     * setup function to run, or a set of properties. If this is a
     * function that function is run synchronously. Any exception in
     * the function will set the overall harness status to `ERROR`.
     * @param {SettingsObject} maybeProperties - An object containing
     * the settings to use, if the first argument is a function.
     *
     */
    function setup(func_or_properties, maybe_properties) {
      var func = null;
      var properties = {};
      if (arguments.length === 2) {
        func = func_or_properties;
        properties = maybe_properties;
      } else if (func_or_properties instanceof Function) {
        func = func_or_properties;
      } else {
        properties = func_or_properties;
      }
      tests.setup(func, properties);
      test_environment.on_new_harness_properties(properties);
    }

    /**
     * Configure the harness, waiting for a promise to resolve
     * before running any `promise_test` tests.
     *
     * @param {Function} func - Function returning a promise that's
     * run synchronously. Promise tests are not run until after this
     * function has resolved.
     * @param {SettingsObject} [properties] - An object containing
     * the harness settings to use.
     *
     */
    function promise_setup(func, properties = {}) {
      if (typeof func !== "function") {
        tests.set_status(
          tests.status.ERROR,
          "promise_test invoked without a function"
        );
        tests.complete();
        return;
      }
      tests.promise_setup_called = true;

      if (!tests.promise_tests) {
        tests.promise_tests = Promise.resolve();
      }

      tests.promise_tests = tests.promise_tests
        .then(function () {
          var result;

          tests.setup(null, properties);
          result = func();
          test_environment.on_new_harness_properties(properties);

          if (!result || typeof result.then !== "function") {
            throw "Non-thenable returned by function passed to `promise_setup`";
          }
          return result;
        })
        .catch(function (e) {
          tests.set_status(tests.status.ERROR, String(e), e && e.stack);
          tests.complete();
        });
    }

    /**
     * Mark test loading as complete.
     *
     * Typically this function is called implicitly on page load; it's
     * only necessary for users to call this when either the
     * ``explicit_done`` or ``single_page`` properties have been set
     * via the :js:func:`setup` function.
     *
     * For single page tests this marks the test as complete and sets its status.
     * For other tests, this marks test loading as complete, but doesn't affect ongoing tests.
     */
    function done() {
      if (tests.tests.length === 0) {
        // `done` is invoked after handling uncaught exceptions, so if the
        // harness status is already set, the corresponding message is more
        // descriptive than the generic message defined here.
        if (tests.status.status === null) {
          tests.status.status = tests.status.ERROR;
          tests.status.message =
            "done() was called without first defining any tests";
        }

        tests.complete();
        return;
      }
      if (tests.file_is_test) {
        // file is test files never have asynchronous cleanup logic,
        // meaning the fully-synchronous `done` function can be used here.
        tests.tests[0].done();
      }
      tests.end_wait();
    }

    /**
     * @deprecated generate a list of tests from a function and list of arguments
     *
     * This is deprecated because it runs all the tests outside of the test functions
     * and as a result any test throwing an exception will result in no tests being
     * run. In almost all cases, you should simply call test within the loop you would
     * use to generate the parameter list array.
     *
     * @param {Function} func - The function that will be called for each generated tests.
     * @param {Any[][]} args - An array of arrays. Each nested array
     * has the structure `[testName, ...testArgs]`. For each of these nested arrays
     * array, a test is generated with name `testName` and test function equivalent to
     * `func(..testArgs)`.
     */
    function generate_tests(func, args, properties) {
      forEach(args, function (x, i) {
        var name = x[0];
        test(
          function () {
            func.apply(this, x.slice(1));
          },
          name,
          Array.isArray(properties) ? properties[i] : properties
        );
      });
    }

    /**
     * @deprecated
     *
     * Register a function as a DOM event listener to the
     * given object for the event bubbling phase.
     *
     * @param {EventTarget} object - Event target
     * @param {string} event - Event name
     * @param {Function} callback - Event handler.
     */
    function on_event(object, event, callback) {
      object.addEventListener(event, callback, false);
    }

    // Internal helper function to provide timeout-like functionality in
    // environments where there is no setTimeout(). (No timeout ID or
    // clearTimeout().)
    function fake_set_timeout(callback, delay) {
      var p = Promise.resolve();
      var start = Date.now();
      var end = start + delay;
      function check() {
        if (end - Date.now() > 0) {
          p.then(check);
        } else {
          callback();
        }
      }
      p.then(check);
    }

    /**
     * Global version of :js:func:`Test.step_timeout` for use in single page tests.
     *
     * @param {Function} func - Function to run after the timeout
     * @param {number} timeout - Time in ms to wait before running the
     * test step. The actual wait time is ``timeout`` x
     * ``timeout_multiplier``.
     */
    function step_timeout(func, timeout) {
      var outer_this = this;
      var args = Array.prototype.slice.call(arguments, 2);
      var local_set_timeout =
        typeof global_scope.setTimeout === "undefined"
          ? fake_set_timeout
          : setTimeout;
      return local_set_timeout(function () {
        func.apply(outer_this, args);
      }, timeout * tests.timeout_multiplier);
    }

    expose(test, "test");
    expose(async_test, "async_test");
    expose(promise_test, "promise_test");
    expose(promise_rejects_js, "promise_rejects_js");
    expose(promise_rejects_dom, "promise_rejects_dom");
    expose(promise_rejects_exactly, "promise_rejects_exactly");
    expose(generate_tests, "generate_tests");
    expose(setup, "setup");
    expose(promise_setup, "promise_setup");
    expose(done, "done");
    expose(on_event, "on_event");
    expose(step_timeout, "step_timeout");

    /*
     * Return a string truncated to the given length, with ... added at the end
     * if it was longer.
     */
    function truncate(s, len) {
      if (s.length > len) {
        return s.substring(0, len - 3) + "...";
      }
      return s;
    }

    /*
     * Return true if object is probably a Node object.
     */
    function is_node(object) {
      // I use duck-typing instead of instanceof, because
      // instanceof doesn't work if the node is from another window (like an
      // iframe's contentWindow):
      // http://www.w3.org/Bugs/Public/show_bug.cgi?id=12295
      try {
        var has_node_properties =
          "nodeType" in object &&
          "nodeName" in object &&
          "nodeValue" in object &&
          "childNodes" in object;
      } catch (e) {
        // We're probably cross-origin, which means we aren't a node
        return false;
      }

      if (has_node_properties) {
        try {
          object.nodeType;
        } catch (e) {
          // The object is probably Node.prototype or another prototype
          // object that inherits from it, and not a Node instance.
          return false;
        }
        return true;
      }
      return false;
    }

    var replacements = {
      0: "0",
      1: "x01",
      2: "x02",
      3: "x03",
      4: "x04",
      5: "x05",
      6: "x06",
      7: "x07",
      8: "b",
      9: "t",
      10: "n",
      11: "v",
      12: "f",
      13: "r",
      14: "x0e",
      15: "x0f",
      16: "x10",
      17: "x11",
      18: "x12",
      19: "x13",
      20: "x14",
      21: "x15",
      22: "x16",
      23: "x17",
      24: "x18",
      25: "x19",
      26: "x1a",
      27: "x1b",
      28: "x1c",
      29: "x1d",
      30: "x1e",
      31: "x1f",
      "0xfffd": "ufffd",
      "0xfffe": "ufffe",
      "0xffff": "uffff",
    };

    /**
     * Convert a value to a nice, human-readable string
     *
     * When many JavaScript Object values are coerced to a String, the
     * resulting value will be ``"[object Object]"``. This obscures
     * helpful information, making the coerced value unsuitable for
     * use in assertion messages, test names, and debugging
     * statements. `format_value` produces more distinctive string
     * representations of many kinds of objects, including arrays and
     * the more important DOM Node types. It also translates String
     * values containing control characters to include human-readable
     * representations.
     *
     * @example
     * // "Document node with 2 children"
     * format_value(document);
     * @example
     * // "\"foo\\uffffbar\""
     * format_value("foo\uffffbar");
     * @example
     * // "[-0, Infinity]"
     * format_value([-0, Infinity]);
     * @param {Any} val - The value to convert to a string.
     * @returns {string} - A string representation of ``val``, optimised for human readability.
     */
    function format_value(val, seen) {
      if (!seen) {
        seen = [];
      }
      if (typeof val === "object" && val !== null) {
        if (seen.indexOf(val) >= 0) {
          return "[...]";
        }
        seen.push(val);
      }
      if (Array.isArray(val)) {
        let output = "[";
        if (val.beginEllipsis !== undefined) {
          output += "…, ";
        }
        output += val
          .map(function (x) {
            return format_value(x, seen);
          })
          .join(", ");
        if (val.endEllipsis !== undefined) {
          output += ", …";
        }
        return output + "]";
      }

      switch (typeof val) {
        case "string":
          val = val.replace(/\\/g, "\\\\");
          for (var p in replacements) {
            var replace = "\\" + replacements[p];
            val = val.replace(RegExp(String.fromCharCode(p), "g"), replace);
          }
          return '"' + val.replace(/"/g, '\\"') + '"';
        case "boolean":
        case "undefined":
          return String(val);
        case "number":
          // In JavaScript, -0 === 0 and String(-0) == "0", so we have to
          // special-case.
          if (val === -0 && 1 / val === -Infinity) {
            return "-0";
          }
          return String(val);
        case "object":
          if (val === null) {
            return "null";
          }

          // Special-case Node objects, since those come up a lot in my tests.  I
          // ignore namespaces.
          if (is_node(val)) {
            switch (val.nodeType) {
              case Node.ELEMENT_NODE:
                var ret = "<" + val.localName;
                for (var i = 0; i < val.attributes.length; i++) {
                  ret +=
                    " " +
                    val.attributes[i].name +
                    '="' +
                    val.attributes[i].value +
                    '"';
                }
                ret += ">" + val.innerHTML + "</" + val.localName + ">";
                return "Element node " + truncate(ret, 60);
              case Node.TEXT_NODE:
                return 'Text node "' + truncate(val.data, 60) + '"';
              case Node.PROCESSING_INSTRUCTION_NODE:
                return (
                  "ProcessingInstruction node with target " +
                  format_value(truncate(val.target, 60)) +
                  " and data " +
                  format_value(truncate(val.data, 60))
                );
              case Node.COMMENT_NODE:
                return "Comment node <!--" + truncate(val.data, 60) + "-->";
              case Node.DOCUMENT_NODE:
                return (
                  "Document node with " +
                  val.childNodes.length +
                  (val.childNodes.length == 1 ? " child" : " children")
                );
              case Node.DOCUMENT_TYPE_NODE:
                return "DocumentType node";
              case Node.DOCUMENT_FRAGMENT_NODE:
                return (
                  "DocumentFragment node with " +
                  val.childNodes.length +
                  (val.childNodes.length == 1 ? " child" : " children")
                );
              default:
                return "Node object of unknown type";
            }
          }

        /* falls through */
        default:
          try {
            return typeof val + ' "' + truncate(String(val), 1000) + '"';
          } catch (e) {
            return (
              "[stringifying object threw " +
              String(e) +
              " with type " +
              String(typeof e) +
              "]"
            );
          }
      }
    }
    expose(format_value, "format_value");

    /*
     * Assertions
     */

    function expose_assert(f, name) {
      function assert_wrapper(...args) {
        let status = Test.statuses.TIMEOUT;
        let stack = null;
        let new_assert_index = null;
        try {
          if (settings.debug) {
            console.debug(
              "ASSERT",
              name,
              tests.current_test && tests.current_test.name,
              args
            );
          }
          if (tests.output) {
            tests.set_assert(name, args);
            // Remember the newly pushed assert's index, because `apply`
            // below might push new asserts.
            new_assert_index = tests.asserts_run.length - 1;
          }
          const rv = f.apply(undefined, args);
          status = Test.statuses.PASS;
          return rv;
        } catch (e) {
          status = Test.statuses.FAIL;
          stack = e.stack ? e.stack : null;
          throw e;
        } finally {
          if (tests.output && !stack) {
            stack = get_stack();
          }
          if (tests.output) {
            tests.set_assert_status(new_assert_index, status, stack);
          }
        }
      }
      expose(assert_wrapper, name);
    }

    /**
     * Assert that ``actual`` is strictly true
     *
     * @param {Any} actual - Value that is asserted to be true
     * @param {string} [description] - Description of the condition being tested
     */
    function assert_true(actual, description) {
      assert(
        actual === true,
        "assert_true",
        description,
        "expected true got ${actual}",
        { actual: actual }
      );
    }
    expose_assert(assert_true, "assert_true");

    /**
     * Assert that ``actual`` is strictly false
     *
     * @param {Any} actual - Value that is asserted to be false
     * @param {string} [description] - Description of the condition being tested
     */
    function assert_false(actual, description) {
      assert(
        actual === false,
        "assert_false",
        description,
        "expected false got ${actual}",
        { actual: actual }
      );
    }
    expose_assert(assert_false, "assert_false");

    function same_value(x, y) {
      if (y !== y) {
        //NaN case
        return x !== x;
      }
      if (x === 0 && y === 0) {
        //Distinguish +0 and -0
        return 1 / x === 1 / y;
      }
      return x === y;
    }

    /**
     * Assert that ``actual`` is the same value as ``expected``.
     *
     * For objects this compares by object identity; for primitives
     * this distinguishes between 0 and -0, and has correct handling
     * of NaN.
     *
     * @param {Any} actual - Test value.
     * @param {Any} expected - Expected value.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_equals(actual, expected, description) {
      /*
       * Test if two primitives are equal or two objects
       * are the same object
       */
      if (typeof actual != typeof expected) {
        assert(
          false,
          "assert_equals",
          description,
          "expected (" +
            typeof expected +
            ") ${expected} but got (" +
            typeof actual +
            ") ${actual}",
          { expected: expected, actual: actual }
        );
        return;
      }
      assert(
        same_value(actual, expected),
        "assert_equals",
        description,
        "expected ${expected} but got ${actual}",
        { expected: expected, actual: actual }
      );
    }
    expose_assert(assert_equals, "assert_equals");

    /**
     * Assert that ``actual`` is not the same value as ``expected``.
     *
     * Comparison is as for :js:func:`assert_equals`.
     *
     * @param {Any} actual - Test value.
     * @param {Any} expected - The value ``actual`` is expected to be different to.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_not_equals(actual, expected, description) {
      assert(
        !same_value(actual, expected),
        "assert_not_equals",
        description,
        "got disallowed value ${actual}",
        { actual: actual }
      );
    }
    expose_assert(assert_not_equals, "assert_not_equals");

    /**
     * Assert that ``expected`` is an array and ``actual`` is one of the members.
     * This is implemented using ``indexOf``, so doesn't handle NaN or ±0 correctly.
     *
     * @param {Any} actual - Test value.
     * @param {Array} expected - An array that ``actual`` is expected to
     * be a member of.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_in_array(actual, expected, description) {
      assert(
        expected.indexOf(actual) != -1,
        "assert_in_array",
        description,
        "value ${actual} not in array ${expected}",
        { actual: actual, expected: expected }
      );
    }
    expose_assert(assert_in_array, "assert_in_array");

    // This function was deprecated in July of 2015.
    // See https://github.com/web-platform-tests/wpt/issues/2033
    /**
     * @deprecated
     * Recursively compare two objects for equality.
     *
     * See `Issue 2033
     * <https://github.com/web-platform-tests/wpt/issues/2033>`_ for
     * more information.
     *
     * @param {Object} actual - Test value.
     * @param {Object} expected - Expected value.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_object_equals(actual, expected, description) {
      assert(
        typeof actual === "object" && actual !== null,
        "assert_object_equals",
        description,
        "value is ${actual}, expected object",
        { actual: actual }
      );
      //This needs to be improved a great deal
      function check_equal(actual, expected, stack) {
        stack.push(actual);

        var p;
        for (p in actual) {
          assert(
            expected.hasOwnProperty(p),
            "assert_object_equals",
            description,
            "unexpected property ${p}",
            { p: p }
          );

          if (typeof actual[p] === "object" && actual[p] !== null) {
            if (stack.indexOf(actual[p]) === -1) {
              check_equal(actual[p], expected[p], stack);
            }
          } else {
            assert(
              same_value(actual[p], expected[p]),
              "assert_object_equals",
              description,
              "property ${p} expected ${expected} got ${actual}",
              { p: p, expected: expected[p], actual: actual[p] }
            );
          }
        }
        for (p in expected) {
          assert(
            actual.hasOwnProperty(p),
            "assert_object_equals",
            description,
            "expected property ${p} missing",
            { p: p }
          );
        }
        stack.pop();
      }
      check_equal(actual, expected, []);
    }
    expose_assert(assert_object_equals, "assert_object_equals");

    /**
     * Assert that ``actual`` and ``expected`` are both arrays, and that the array properties of
     * ``actual`` and ``expected`` are all the same value (as for :js:func:`assert_equals`).
     *
     * @param {Array} actual - Test array.
     * @param {Array} expected - Array that is expected to contain the same values as ``actual``.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_array_equals(actual, expected, description) {
      const max_array_length = 20;
      function shorten_array(arr, offset = 0) {
        // Make ", …" only show up when it would likely reduce the length, not accounting for
        // fonts.
        if (arr.length < max_array_length + 2) {
          return arr;
        }
        // By default we want half the elements after the offset and half before
        // But if that takes us past the end of the array, we have more before, and
        // if it takes us before the start we have more after.
        const length_after_offset = Math.floor(max_array_length / 2);
        let upper_bound = Math.min(length_after_offset + offset, arr.length);
        const lower_bound = Math.max(upper_bound - max_array_length, 0);

        if (lower_bound === 0) {
          upper_bound = max_array_length;
        }

        const output = arr.slice(lower_bound, upper_bound);
        if (lower_bound > 0) {
          output.beginEllipsis = true;
        }
        if (upper_bound < arr.length) {
          output.endEllipsis = true;
        }
        return output;
      }

      assert(
        typeof actual === "object" && actual !== null && "length" in actual,
        "assert_array_equals",
        description,
        "value is ${actual}, expected array",
        { actual: actual }
      );
      assert(
        actual.length === expected.length,
        "assert_array_equals",
        description,
        "lengths differ, expected array ${expected} length ${expectedLength}, got ${actual} length ${actualLength}",
        {
          expected: shorten_array(expected, expected.length - 1),
          expectedLength: expected.length,
          actual: shorten_array(actual, actual.length - 1),
          actualLength: actual.length,
        }
      );

      for (var i = 0; i < actual.length; i++) {
        assert(
          actual.hasOwnProperty(i) === expected.hasOwnProperty(i),
          "assert_array_equals",
          description,
          "expected property ${i} to be ${expected} but was ${actual} (expected array ${arrayExpected} got ${arrayActual})",
          {
            i: i,
            expected: expected.hasOwnProperty(i) ? "present" : "missing",
            actual: actual.hasOwnProperty(i) ? "present" : "missing",
            arrayExpected: shorten_array(expected, i),
            arrayActual: shorten_array(actual, i),
          }
        );
        assert(
          same_value(expected[i], actual[i]),
          "assert_array_equals",
          description,
          "expected property ${i} to be ${expected} but got ${actual} (expected array ${arrayExpected} got ${arrayActual})",
          {
            i: i,
            expected: expected[i],
            actual: actual[i],
            arrayExpected: shorten_array(expected, i),
            arrayActual: shorten_array(actual, i),
          }
        );
      }
    }
    expose_assert(assert_array_equals, "assert_array_equals");

    /**
     * Assert that each array property in ``actual`` is a number within
     * ± `epsilon` of the corresponding property in `expected`.
     *
     * @param {Array} actual - Array of test values.
     * @param {Array} expected - Array of values expected to be close to the values in ``actual``.
     * @param {number} epsilon - Magnitude of allowed difference
     * between each value in ``actual`` and ``expected``.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_array_approx_equals(
      actual,
      expected,
      epsilon,
      description
    ) {
      /*
       * Test if two primitive arrays are equal within +/- epsilon
       */
      assert(
        actual.length === expected.length,
        "assert_array_approx_equals",
        description,
        "lengths differ, expected ${expected} got ${actual}",
        { expected: expected.length, actual: actual.length }
      );

      for (var i = 0; i < actual.length; i++) {
        assert(
          actual.hasOwnProperty(i) === expected.hasOwnProperty(i),
          "assert_array_approx_equals",
          description,
          "property ${i}, property expected to be ${expected} but was ${actual}",
          {
            i: i,
            expected: expected.hasOwnProperty(i) ? "present" : "missing",
            actual: actual.hasOwnProperty(i) ? "present" : "missing",
          }
        );
        assert(
          typeof actual[i] === "number",
          "assert_array_approx_equals",
          description,
          "property ${i}, expected a number but got a ${type_actual}",
          { i: i, type_actual: typeof actual[i] }
        );
        assert(
          Math.abs(actual[i] - expected[i]) <= epsilon,
          "assert_array_approx_equals",
          description,
          "property ${i}, expected ${expected} +/- ${epsilon}, expected ${expected} but got ${actual}",
          { i: i, expected: expected[i], actual: actual[i], epsilon: epsilon }
        );
      }
    }
    expose_assert(assert_array_approx_equals, "assert_array_approx_equals");

    /**
     * Assert that ``actual`` is within ± ``epsilon`` of ``expected``.
     *
     * @param {number} actual - Test value.
     * @param {number} expected - Value number is expected to be close to.
     * @param {number} epsilon - Magnitude of allowed difference between ``actual`` and ``expected``.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_approx_equals(actual, expected, epsilon, description) {
      /*
       * Test if two primitive numbers are equal within +/- epsilon
       */
      assert(
        typeof actual === "number",
        "assert_approx_equals",
        description,
        "expected a number but got a ${type_actual}",
        { type_actual: typeof actual }
      );

      // The epsilon math below does not place nice with NaN and Infinity
      // But in this case Infinity = Infinity and NaN = NaN
      if (isFinite(actual) || isFinite(expected)) {
        assert(
          Math.abs(actual - expected) <= epsilon,
          "assert_approx_equals",
          description,
          "expected ${expected} +/- ${epsilon} but got ${actual}",
          { expected: expected, actual: actual, epsilon: epsilon }
        );
      } else {
        assert_equals(actual, expected);
      }
    }
    expose_assert(assert_approx_equals, "assert_approx_equals");

    /**
     * Assert that ``actual`` is a number less than ``expected``.
     *
     * @param {number} actual - Test value.
     * @param {number} expected - Number that ``actual`` must be less than.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_less_than(actual, expected, description) {
      /*
       * Test if a primitive number is less than another
       */
      assert(
        typeof actual === "number",
        "assert_less_than",
        description,
        "expected a number but got a ${type_actual}",
        { type_actual: typeof actual }
      );

      assert(
        actual < expected,
        "assert_less_than",
        description,
        "expected a number less than ${expected} but got ${actual}",
        { expected: expected, actual: actual }
      );
    }
    expose_assert(assert_less_than, "assert_less_than");

    /**
     * Assert that ``actual`` is a number greater than ``expected``.
     *
     * @param {number} actual - Test value.
     * @param {number} expected - Number that ``actual`` must be greater than.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_greater_than(actual, expected, description) {
      /*
       * Test if a primitive number is greater than another
       */
      assert(
        typeof actual === "number",
        "assert_greater_than",
        description,
        "expected a number but got a ${type_actual}",
        { type_actual: typeof actual }
      );

      assert(
        actual > expected,
        "assert_greater_than",
        description,
        "expected a number greater than ${expected} but got ${actual}",
        { expected: expected, actual: actual }
      );
    }
    expose_assert(assert_greater_than, "assert_greater_than");

    /**
     * Assert that ``actual`` is a number greater than ``lower`` and less
     * than ``upper`` but not equal to either.
     *
     * @param {number} actual - Test value.
     * @param {number} lower - Number that ``actual`` must be greater than.
     * @param {number} upper - Number that ``actual`` must be less than.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_between_exclusive(actual, lower, upper, description) {
      /*
       * Test if a primitive number is between two others
       */
      assert(
        typeof actual === "number",
        "assert_between_exclusive",
        description,
        "expected a number but got a ${type_actual}",
        { type_actual: typeof actual }
      );

      assert(
        actual > lower && actual < upper,
        "assert_between_exclusive",
        description,
        "expected a number greater than ${lower} " +
          "and less than ${upper} but got ${actual}",
        { lower: lower, upper: upper, actual: actual }
      );
    }
    expose_assert(assert_between_exclusive, "assert_between_exclusive");

    /**
     * Assert that ``actual`` is a number less than or equal to ``expected``.
     *
     * @param {number} actual - Test value.
     * @param {number} expected - Number that ``actual`` must be less
     * than or equal to.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_less_than_equal(actual, expected, description) {
      /*
       * Test if a primitive number is less than or equal to another
       */
      assert(
        typeof actual === "number",
        "assert_less_than_equal",
        description,
        "expected a number but got a ${type_actual}",
        { type_actual: typeof actual }
      );

      assert(
        actual <= expected,
        "assert_less_than_equal",
        description,
        "expected a number less than or equal to ${expected} but got ${actual}",
        { expected: expected, actual: actual }
      );
    }
    expose_assert(assert_less_than_equal, "assert_less_than_equal");

    /**
     * Assert that ``actual`` is a number greater than or equal to ``expected``.
     *
     * @param {number} actual - Test value.
     * @param {number} expected - Number that ``actual`` must be greater
     * than or equal to.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_greater_than_equal(actual, expected, description) {
      /*
       * Test if a primitive number is greater than or equal to another
       */
      assert(
        typeof actual === "number",
        "assert_greater_than_equal",
        description,
        "expected a number but got a ${type_actual}",
        { type_actual: typeof actual }
      );

      assert(
        actual >= expected,
        "assert_greater_than_equal",
        description,
        "expected a number greater than or equal to ${expected} but got ${actual}",
        { expected: expected, actual: actual }
      );
    }
    expose_assert(assert_greater_than_equal, "assert_greater_than_equal");

    /**
     * Assert that ``actual`` is a number greater than or equal to ``lower`` and less
     * than or equal to ``upper``.
     *
     * @param {number} actual - Test value.
     * @param {number} lower - Number that ``actual`` must be greater than or equal to.
     * @param {number} upper - Number that ``actual`` must be less than or equal to.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_between_inclusive(actual, lower, upper, description) {
      /*
       * Test if a primitive number is between to two others or equal to either of them
       */
      assert(
        typeof actual === "number",
        "assert_between_inclusive",
        description,
        "expected a number but got a ${type_actual}",
        { type_actual: typeof actual }
      );

      assert(
        actual >= lower && actual <= upper,
        "assert_between_inclusive",
        description,
        "expected a number greater than or equal to ${lower} " +
          "and less than or equal to ${upper} but got ${actual}",
        { lower: lower, upper: upper, actual: actual }
      );
    }
    expose_assert(assert_between_inclusive, "assert_between_inclusive");

    /**
     * Assert that ``actual`` matches the RegExp ``expected``.
     *
     * @param {String} actual - Test string.
     * @param {RegExp} expected - RegExp ``actual`` must match.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_regexp_match(actual, expected, description) {
      /*
       * Test if a string (actual) matches a regexp (expected)
       */
      assert(
        expected.test(actual),
        "assert_regexp_match",
        description,
        "expected ${expected} but got ${actual}",
        { expected: expected, actual: actual }
      );
    }
    expose_assert(assert_regexp_match, "assert_regexp_match");

    /**
     * Assert that the class string of ``object`` as returned in
     * ``Object.prototype.toString`` is equal to ``class_name``.
     *
     * @param {Object} object - Object to stringify.
     * @param {string} class_string - Expected class string for ``object``.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_class_string(object, class_string, description) {
      var actual = {}.toString.call(object);
      var expected = "[object " + class_string + "]";
      assert(
        same_value(actual, expected),
        "assert_class_string",
        description,
        "expected ${expected} but got ${actual}",
        { expected: expected, actual: actual }
      );
    }
    expose_assert(assert_class_string, "assert_class_string");

    /**
     * Assert that ``object`` has an own property with name ``property_name``.
     *
     * @param {Object} object - Object that should have the given property.
     * @param {string} property_name - Expected property name.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_own_property(object, property_name, description) {
      assert(
        object.hasOwnProperty(property_name),
        "assert_own_property",
        description,
        "expected property ${p} missing",
        { p: property_name }
      );
    }
    expose_assert(assert_own_property, "assert_own_property");

    /**
     * Assert that ``object`` does not have an own property with name ``property_name``.
     *
     * @param {Object} object - Object that should not have the given property.
     * @param {string} property_name - Property name to test.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_not_own_property(object, property_name, description) {
      assert(
        !object.hasOwnProperty(property_name),
        "assert_not_own_property",
        description,
        "unexpected property ${p} is found on object",
        { p: property_name }
      );
    }
    expose_assert(assert_not_own_property, "assert_not_own_property");

    function _assert_inherits(name) {
      return function (object, property_name, description) {
        assert(
          (typeof object === "object" && object !== null) ||
            typeof object === "function" ||
            // Or has [[IsHTMLDDA]] slot
            String(object) === "[object HTMLAllCollection]",
          name,
          description,
          "provided value is not an object"
        );

        assert(
          "hasOwnProperty" in object,
          name,
          description,
          "provided value is an object but has no hasOwnProperty method"
        );

        assert(
          !object.hasOwnProperty(property_name),
          name,
          description,
          "property ${p} found on object expected in prototype chain",
          { p: property_name }
        );

        assert(
          property_name in object,
          name,
          description,
          "property ${p} not found in prototype chain",
          { p: property_name }
        );
      };
    }

    /**
     * Assert that ``object`` does not have an own property with name
     * ``property_name``, but inherits one through the prototype chain.
     *
     * @param {Object} object - Object that should have the given property in its prototype chain.
     * @param {string} property_name - Expected property name.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_inherits(object, property_name, description) {
      return _assert_inherits("assert_inherits")(
        object,
        property_name,
        description
      );
    }
    expose_assert(assert_inherits, "assert_inherits");

    /**
     * Alias for :js:func:`insert_inherits`.
     *
     * @param {Object} object - Object that should have the given property in its prototype chain.
     * @param {string} property_name - Expected property name.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_idl_attribute(object, property_name, description) {
      return _assert_inherits("assert_idl_attribute")(
        object,
        property_name,
        description
      );
    }
    expose_assert(assert_idl_attribute, "assert_idl_attribute");

    /**
     * Assert that ``object`` has a property named ``property_name`` and that the property is readonly.
     *
     * Note: The implementation tries to update the named property, so
     * any side effects of updating will be triggered. Users are
     * encouraged to instead inspect the property descriptor of ``property_name`` on ``object``.
     *
     * @param {Object} object - Object that should have the given property in its prototype chain.
     * @param {string} property_name - Expected property name.
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_readonly(object, property_name, description) {
      var initial_value = object[property_name];
      try {
        //Note that this can have side effects in the case where
        //the property has PutForwards
        object[property_name] = initial_value + "a"; //XXX use some other value here?
        assert(
          same_value(object[property_name], initial_value),
          "assert_readonly",
          description,
          "changing property ${p} succeeded",
          { p: property_name }
        );
      } finally {
        object[property_name] = initial_value;
      }
    }
    expose_assert(assert_readonly, "assert_readonly");

    /**
     * Assert a JS Error with the expected constructor is thrown.
     *
     * @param {object} constructor The expected exception constructor.
     * @param {Function} func Function which should throw.
     * @param {string} [description] Error description for the case that the error is not thrown.
     */
    function assert_throws_js(constructor, func, description) {
      assert_throws_js_impl(constructor, func, description, "assert_throws_js");
    }
    expose_assert(assert_throws_js, "assert_throws_js");

    /**
     * Like assert_throws_js but allows specifying the assertion type
     * (assert_throws_js or promise_rejects_js, in practice).
     */
    function assert_throws_js_impl(
      constructor,
      func,
      description,
      assertion_type
    ) {
      try {
        func.call(this);
        assert(false, assertion_type, description, "${func} did not throw", {
          func: func,
        });
      } catch (e) {
        if (e instanceof AssertionError) {
          throw e;
        }

        // Basic sanity-checks on the thrown exception.
        assert(
          typeof e === "object",
          assertion_type,
          description,
          "${func} threw ${e} with type ${type}, not an object",
          { func: func, e: e, type: typeof e }
        );

        assert(
          e !== null,
          assertion_type,
          description,
          "${func} threw null, not an object",
          { func: func }
        );

        // Basic sanity-check on the passed-in constructor
        assert(
          typeof constructor == "function",
          assertion_type,
          description,
          "${constructor} is not a constructor",
          { constructor: constructor }
        );
        var obj = constructor;
        while (obj) {
          if (typeof obj === "function" && obj.name === "Error") {
            break;
          }
          obj = Object.getPrototypeOf(obj);
        }
        assert(
          obj != null,
          assertion_type,
          description,
          "${constructor} is not an Error subtype",
          { constructor: constructor }
        );

        // And checking that our exception is reasonable
        assert(
          e.constructor === constructor && e.name === constructor.name,
          assertion_type,
          description,
          "${func} threw ${actual} (${actual_name}) expected instance of ${expected} (${expected_name})",
          {
            func: func,
            actual: e,
            actual_name: e.name,
            expected: constructor,
            expected_name: constructor.name,
          }
        );
      }
    }

    // TODO: Figure out how to document the overloads better.
    // sphinx-js doesn't seem to handle @variation correctly,
    // and only expects a single JSDoc entry per function.
    /**
     * Assert a DOMException with the expected type is thrown.
     *
     * There are two ways of calling assert_throws_dom:
     *
     * 1) If the DOMException is expected to come from the current global, the
     * second argument should be the function expected to throw and a third,
     * optional, argument is the assertion description.
     *
     * 2) If the DOMException is expected to come from some other global, the
     * second argument should be the DOMException constructor from that global,
     * the third argument the function expected to throw, and the fourth, optional,
     * argument the assertion description.
     *
     * @param {number|string} type - The expected exception name or
     * code.  See the `table of names and codes
     * <https://webidl.spec.whatwg.org/#dfn-error-names-table>`_. If a
     * number is passed it should be one of the numeric code values in
     * that table (e.g. 3, 4, etc).  If a string is passed it can
     * either be an exception name (e.g. "HierarchyRequestError",
     * "WrongDocumentError") or the name of the corresponding error
     * code (e.g. "``HIERARCHY_REQUEST_ERR``", "``WRONG_DOCUMENT_ERR``").
     * @param {Function} descriptionOrFunc - The function expected to
     * throw (if the exception comes from another global), or the
     * optional description of the condition being tested (if the
     * exception comes from the current global).
     * @param {string} [description] - Description of the condition
     * being tested (if the exception comes from another global).
     *
     */
    function assert_throws_dom(
      type,
      funcOrConstructor,
      descriptionOrFunc,
      maybeDescription
    ) {
      let constructor, func, description;
      if (funcOrConstructor.name === "DOMException") {
        constructor = funcOrConstructor;
        func = descriptionOrFunc;
        description = maybeDescription;
      } else {
        constructor = self.DOMException;
        func = funcOrConstructor;
        description = descriptionOrFunc;
        assert(
          maybeDescription === undefined,
          "Too many args passed to no-constructor version of assert_throws_dom, or accidentally explicitly passed undefined"
        );
      }
      assert_throws_dom_impl(
        type,
        func,
        description,
        "assert_throws_dom",
        constructor
      );
    }
    expose_assert(assert_throws_dom, "assert_throws_dom");

    /**
     * Similar to assert_throws_dom but allows specifying the assertion type
     * (assert_throws_dom or promise_rejects_dom, in practice).  The
     * "constructor" argument must be the DOMException constructor from the
     * global we expect the exception to come from.
     */
    function assert_throws_dom_impl(
      type,
      func,
      description,
      assertion_type,
      constructor
    ) {
      try {
        func.call(this);
        assert(false, assertion_type, description, "${func} did not throw", {
          func: func,
        });
      } catch (e) {
        if (e instanceof AssertionError) {
          throw e;
        }

        // Basic sanity-checks on the thrown exception.
        assert(
          typeof e === "object",
          assertion_type,
          description,
          "${func} threw ${e} with type ${type}, not an object",
          { func: func, e: e, type: typeof e }
        );

        assert(
          e !== null,
          assertion_type,
          description,
          "${func} threw null, not an object",
          { func: func }
        );

        // Sanity-check our type
        assert(
          typeof type == "number" || typeof type == "string",
          assertion_type,
          description,
          "${type} is not a number or string",
          { type: type }
        );

        var codename_name_map = {
          INDEX_SIZE_ERR: "IndexSizeError",
          HIERARCHY_REQUEST_ERR: "HierarchyRequestError",
          WRONG_DOCUMENT_ERR: "WrongDocumentError",
          INVALID_CHARACTER_ERR: "InvalidCharacterError",
          NO_MODIFICATION_ALLOWED_ERR: "NoModificationAllowedError",
          NOT_FOUND_ERR: "NotFoundError",
          NOT_SUPPORTED_ERR: "NotSupportedError",
          INUSE_ATTRIBUTE_ERR: "InUseAttributeError",
          INVALID_STATE_ERR: "InvalidStateError",
          SYNTAX_ERR: "SyntaxError",
          INVALID_MODIFICATION_ERR: "InvalidModificationError",
          NAMESPACE_ERR: "NamespaceError",
          INVALID_ACCESS_ERR: "InvalidAccessError",
          TYPE_MISMATCH_ERR: "TypeMismatchError",
          SECURITY_ERR: "SecurityError",
          NETWORK_ERR: "NetworkError",
          ABORT_ERR: "AbortError",
          URL_MISMATCH_ERR: "URLMismatchError",
          QUOTA_EXCEEDED_ERR: "QuotaExceededError",
          TIMEOUT_ERR: "TimeoutError",
          INVALID_NODE_TYPE_ERR: "InvalidNodeTypeError",
          DATA_CLONE_ERR: "DataCloneError",
        };

        var name_code_map = {
          IndexSizeError: 1,
          HierarchyRequestError: 3,
          WrongDocumentError: 4,
          InvalidCharacterError: 5,
          NoModificationAllowedError: 7,
          NotFoundError: 8,
          NotSupportedError: 9,
          InUseAttributeError: 10,
          InvalidStateError: 11,
          SyntaxError: 12,
          InvalidModificationError: 13,
          NamespaceError: 14,
          InvalidAccessError: 15,
          TypeMismatchError: 17,
          SecurityError: 18,
          NetworkError: 19,
          AbortError: 20,
          URLMismatchError: 21,
          QuotaExceededError: 22,
          TimeoutError: 23,
          InvalidNodeTypeError: 24,
          DataCloneError: 25,

          EncodingError: 0,
          NotReadableError: 0,
          UnknownError: 0,
          ConstraintError: 0,
          DataError: 0,
          TransactionInactiveError: 0,
          ReadOnlyError: 0,
          VersionError: 0,
          OperationError: 0,
          NotAllowedError: 0,
          OptOutError: 0,
        };

        var code_name_map = {};
        for (var key in name_code_map) {
          if (name_code_map[key] > 0) {
            code_name_map[name_code_map[key]] = key;
          }
        }

        var required_props = {};
        var name;

        if (typeof type === "number") {
          if (type === 0) {
            throw new AssertionError(
              "Test bug: ambiguous DOMException code 0 passed to assert_throws_dom()"
            );
          } else if (!(type in code_name_map)) {
            throw new AssertionError(
              'Test bug: unrecognized DOMException code "' +
                type +
                '" passed to assert_throws_dom()'
            );
          }
          name = code_name_map[type];
          required_props.code = type;
        } else if (typeof type === "string") {
          name = type in codename_name_map ? codename_name_map[type] : type;
          if (!(name in name_code_map)) {
            throw new AssertionError(
              'Test bug: unrecognized DOMException code name or name "' +
                type +
                '" passed to assert_throws_dom()'
            );
          }

          required_props.code = name_code_map[name];
        }

        if (
          required_props.code === 0 ||
          ("name" in e &&
            e.name !== e.name.toUpperCase() &&
            e.name !== "DOMException")
        ) {
          // New style exception: also test the name property.
          required_props.name = name;
        }

        for (var prop in required_props) {
          assert(
            prop in e && e[prop] == required_props[prop],
            assertion_type,
            description,
            "${func} threw ${e} that is not a DOMException " +
              type +
              ": property ${prop} is equal to ${actual}, expected ${expected}",
            {
              func: func,
              e: e,
              prop: prop,
              actual: e[prop],
              expected: required_props[prop],
            }
          );
        }

        // Check that the exception is from the right global.  This check is last
        // so more specific, and more informative, checks on the properties can
        // happen in case a totally incorrect exception is thrown.
        assert(
          e.constructor === constructor,
          assertion_type,
          description,
          "${func} threw an exception from the wrong global",
          { func }
        );
      }
    }

    /**
     * Assert the provided value is thrown.
     *
     * @param {value} exception The expected exception.
     * @param {Function} func Function which should throw.
     * @param {string} [description] Error description for the case that the error is not thrown.
     */
    function assert_throws_exactly(exception, func, description) {
      assert_throws_exactly_impl(
        exception,
        func,
        description,
        "assert_throws_exactly"
      );
    }
    expose_assert(assert_throws_exactly, "assert_throws_exactly");

    /**
     * Like assert_throws_exactly but allows specifying the assertion type
     * (assert_throws_exactly or promise_rejects_exactly, in practice).
     */
    function assert_throws_exactly_impl(
      exception,
      func,
      description,
      assertion_type
    ) {
      try {
        func.call(this);
        assert(false, assertion_type, description, "${func} did not throw", {
          func: func,
        });
      } catch (e) {
        if (e instanceof AssertionError) {
          throw e;
        }

        assert(
          same_value(e, exception),
          assertion_type,
          description,
          "${func} threw ${e} but we expected it to throw ${exception}",
          { func: func, e: e, exception: exception }
        );
      }
    }

    /**
     * Asserts if called. Used to ensure that a specific codepath is
     * not taken e.g. that an error event isn't fired.
     *
     * @param {string} [description] - Description of the condition being tested.
     */
    function assert_unreached(description) {
      assert(
        false,
        "assert_unreached",
        description,
        "Reached unreachable code"
      );
    }
    expose_assert(assert_unreached, "assert_unreached");

    /**
     * @callback AssertFunc
     * @param {Any} actual
     * @param {Any} expected
     * @param {Any[]} args
     */

    /**
     * Asserts that ``actual`` matches at least one value of ``expected``
     * according to a comparison defined by ``assert_func``.
     *
     * Note that tests with multiple allowed pass conditions are bad
     * practice unless the spec specifically allows multiple
     * behaviours. Test authors should not use this method simply to
     * hide UA bugs.
     *
     * @param {AssertFunc} assert_func - Function to compare actual
     * and expected. It must throw when the comparison fails and
     * return when the comparison passes.
     * @param {Any} actual - Test value.
     * @param {Array} expected_array - Array of possible expected values.
     * @param {Any[]} args - Additional arguments to pass to ``assert_func``.
     */
    function assert_any(assert_func, actual, expected_array, ...args) {
      var errors = [];
      var passed = false;
      forEach(expected_array, function (expected) {
        try {
          assert_func.apply(this, [actual, expected].concat(args));
          passed = true;
        } catch (e) {
          errors.push(e.message);
        }
      });
      if (!passed) {
        throw new AssertionError(errors.join("\n\n"));
      }
    }
    // FIXME: assert_any cannot use expose_assert, because assert_wrapper does
    // not support nested assert calls (e.g. to assert_func). We need to
    // support bypassing assert_wrapper for the inner asserts here.
    expose(assert_any, "assert_any");

    /**
     * Assert that a feature is implemented, based on a 'truthy' condition.
     *
     * This function should be used to early-exit from tests in which there is
     * no point continuing without support for a non-optional spec or spec
     * feature. For example:
     *
     *     assert_implements(window.Foo, 'Foo is not supported');
     *
     * @param {object} condition The truthy value to test
     * @param {string} [description] Error description for the case that the condition is not truthy.
     */
    function assert_implements(condition, description) {
      assert(!!condition, "assert_implements", description);
    }
    expose_assert(assert_implements, "assert_implements");

    /**
     * Assert that an optional feature is implemented, based on a 'truthy' condition.
     *
     * This function should be used to early-exit from tests in which there is
     * no point continuing without support for an explicitly optional spec or
     * spec feature. For example:
     *
     *     assert_implements_optional(video.canPlayType("video/webm"),
     *                                "webm video playback not supported");
     *
     * @param {object} condition The truthy value to test
     * @param {string} [description] Error description for the case that the condition is not truthy.
     */
    function assert_implements_optional(condition, description) {
      if (!condition) {
        throw new OptionalFeatureUnsupportedError(description);
      }
    }
    expose_assert(assert_implements_optional, "assert_implements_optional");

    /**
     * @class
     *
     * A single subtest. A Test is not constructed directly but via the
     * :js:func:`test`, :js:func:`async_test` or :js:func:`promise_test` functions.
     *
     * @param {string} name - This must be unique in a given file and must be
     * invariant between runs.
     *
     */
    function Test(name, properties) {
      if (tests.file_is_test && tests.tests.length) {
        throw new Error("Tried to create a test with file_is_test");
      }
      /** The test name. */
      this.name = name;

      this.phase =
        tests.is_aborted || tests.phase === tests.phases.COMPLETE
          ? this.phases.COMPLETE
          : this.phases.INITIAL;

      /** The test status code.*/
      this.status = this.NOTRUN;
      this.timeout_id = null;
      this.index = null;

      this.properties = properties || {};
      this.timeout_length = settings.test_timeout;
      if (this.timeout_length !== null) {
        this.timeout_length *= tests.timeout_multiplier;
      }

      /** A message indicating the reason for test failure. */
      this.message = null;
      /** Stack trace in case of failure. */
      this.stack = null;

      this.steps = [];
      this._is_promise_test = false;

      this.cleanup_callbacks = [];
      this._user_defined_cleanup_count = 0;
      this._done_callbacks = [];

      if (typeof AbortController === "function") {
        this._abortController = new AbortController();
      }

      // Tests declared following harness completion are likely an indication
      // of a programming error, but they cannot be reported
      // deterministically.
      if (tests.phase === tests.phases.COMPLETE) {
        return;
      }

      tests.push(this);
    }

    /**
     * Enum of possible test statuses.
     *
     * :values:
     *   - ``PASS``
     *   - ``FAIL``
     *   - ``TIMEOUT``
     *   - ``NOTRUN``
     *   - ``PRECONDITION_FAILED``
     */
    Test.statuses = {
      PASS: 0,
      FAIL: 1,
      TIMEOUT: 2,
      NOTRUN: 3,
      PRECONDITION_FAILED: 4,
    };

    Test.prototype = merge({}, Test.statuses);

    Test.prototype.phases = {
      INITIAL: 0,
      STARTED: 1,
      HAS_RESULT: 2,
      CLEANING: 3,
      COMPLETE: 4,
    };

    Test.prototype.status_formats = {
      0: "Pass",
      1: "Fail",
      2: "Timeout",
      3: "Not Run",
      4: "Optional Feature Unsupported",
    };

    Test.prototype.format_status = function () {
      return this.status_formats[this.status];
    };

    Test.prototype.structured_clone = function () {
      if (!this._structured_clone) {
        var msg = this.message;
        msg = msg ? String(msg) : msg;
        this._structured_clone = merge(
          {
            name: String(this.name),
            properties: merge({}, this.properties),
            phases: merge({}, this.phases),
          },
          Test.statuses
        );
      }
      this._structured_clone.status = this.status;
      this._structured_clone.message = this.message;
      this._structured_clone.stack = this.stack;
      this._structured_clone.index = this.index;
      this._structured_clone.phase = this.phase;
      return this._structured_clone;
    };

    /**
     * Run a single step of an ongoing test.
     *
     * @param {string} func - Callback function to run as a step. If
     * this throws an :js:func:`AssertionError`, or any other
     * exception, the :js:class:`Test` status is set to ``FAIL``.
     * @param {Object} [this_obj] - The object to use as the this
     * value when calling ``func``. Defaults to the  :js:class:`Test` object.
     */
    Test.prototype.step = function (func, this_obj) {
      if (this.phase > this.phases.STARTED) {
        return;
      }

      if (settings.debug && this.phase !== this.phases.STARTED) {
        console.log("TEST START", this.name);
      }
      this.phase = this.phases.STARTED;
      //If we don't get a result before the harness times out that will be a test timeout
      this.set_status(this.TIMEOUT, "Test timed out");

      tests.started = true;
      tests.current_test = this;
      tests.notify_test_state(this);

      if (this.timeout_id === null) {
        this.set_timeout();
      }

      this.steps.push(func);

      if (arguments.length === 1) {
        this_obj = this;
      }

      if (settings.debug) {
        console.debug("TEST STEP", this.name);
      }

      try {
        return func.apply(this_obj, Array.prototype.slice.call(arguments, 2));
      } catch (e) {
        if (this.phase >= this.phases.HAS_RESULT) {
          return;
        }
        var status =
          e instanceof OptionalFeatureUnsupportedError
            ? this.PRECONDITION_FAILED
            : this.FAIL;
        var message = String(
          typeof e === "object" && e !== null ? e.message : e
        );
        var stack = e.stack ? e.stack : null;

        this.set_status(status, message, stack);
        this.phase = this.phases.HAS_RESULT;
        this.done();
      } finally {
        this.current_test = null;
      }
    };

    /**
     * Wrap a function so that it runs as a step of the current test.
     *
     * This allows creating a callback function that will run as a
     * test step.
     *
     * @example
     * let t = async_test("Example");
     * onload = t.step_func(e => {
     *   assert_equals(e.name, "load");
     *   // Mark the test as complete.
     *   t.done();
     * })
     *
     * @param {string} func - Function to run as a step. If this
     * throws an :js:func:`AssertionError`, or any other exception,
     * the :js:class:`Test` status is set to ``FAIL``.
     * @param {Object} [this_obj] - The object to use as the this
     * value when calling ``func``. Defaults to the :js:class:`Test` object.
     */
    Test.prototype.step_func = function (func, this_obj) {
      var test_this = this;

      if (arguments.length === 1) {
        this_obj = test_this;
      }

      return function () {
        return test_this.step.apply(
          test_this,
          [func, this_obj].concat(Array.prototype.slice.call(arguments))
        );
      };
    };

    /**
     * Wrap a function so that it runs as a step of the current test,
     * and automatically marks the test as complete if the function
     * returns without error.
     *
     * @param {string} func - Function to run as a step. If this
     * throws an :js:func:`AssertionError`, or any other exception,
     * the :js:class:`Test` status is set to ``FAIL``. If it returns
     * without error the status is set to ``PASS``.
     * @param {Object} [this_obj] - The object to use as the this
     * value when calling `func`. Defaults to the :js:class:`Test` object.
     */
    Test.prototype.step_func_done = function (func, this_obj) {
      var test_this = this;

      if (arguments.length === 1) {
        this_obj = test_this;
      }

      return function () {
        if (func) {
          test_this.step.apply(
            test_this,
            [func, this_obj].concat(Array.prototype.slice.call(arguments))
          );
        }
        test_this.done();
      };
    };

    /**
     * Return a function that automatically sets the current test to
     * ``FAIL`` if it's called.
     *
     * @param {string} [description] - Error message to add to assert
     * in case of failure.
     *
     */
    Test.prototype.unreached_func = function (description) {
      return this.step_func(function () {
        assert_unreached(description);
      });
    };

    /**
     * Run a function as a step of the test after a given timeout.
     *
     * This multiplies the timeout by the global timeout multiplier to
     * account for the expected execution speed of the current test
     * environment. For example ``test.step_timeout(f, 2000)`` with a
     * timeout multiplier of 2 will wait for 4000ms before calling ``f``.
     *
     * In general it's encouraged to use :js:func:`Test.step_wait` or
     * :js:func:`step_wait_func` in preference to this function where possible,
     * as they provide better test performance.
     *
     * @param {Function} func - Function to run as a test
     * step.
     * @param {number} timeout - Time in ms to wait before running the
     * test step. The actual wait time is ``timeout`` x
     * ``timeout_multiplier``.
     *
     */
    Test.prototype.step_timeout = function (func, timeout) {
      var test_this = this;
      var args = Array.prototype.slice.call(arguments, 2);
      var local_set_timeout =
        typeof global_scope.setTimeout === "undefined"
          ? fake_set_timeout
          : setTimeout;
      return local_set_timeout(
        this.step_func(function () {
          return func.apply(test_this, args);
        }),
        timeout * tests.timeout_multiplier
      );
    };

    /**
     * Poll for a function to return true, and call a callback
     * function once it does, or assert if a timeout is
     * reached. This is preferred over a simple step_timeout
     * whenever possible since it allows the timeout to be longer
     * to reduce intermittents without compromising test execution
     * speed when the condition is quickly met.
     *
     * @param {Function} cond A function taking no arguments and
     *                        returning a boolean or a Promise. The callback is
     *                        called when this function returns true, or the
     *                        returned Promise is resolved with true.
     * @param {Function} func A function taking no arguments to call once
     *                        the condition is met.
     * @param {string} [description] Error message to add to assert in case of
     *                               failure.
     * @param {number} timeout Timeout in ms. This is multiplied by the global
     *                         timeout_multiplier
     * @param {number} interval Polling interval in ms
     *
     */
    Test.prototype.step_wait_func = function (
      cond,
      func,
      description,
      timeout = 3000,
      interval = 100
    ) {
      var timeout_full = timeout * tests.timeout_multiplier;
      var remaining = Math.ceil(timeout_full / interval);
      var test_this = this;
      var local_set_timeout =
        typeof global_scope.setTimeout === "undefined"
          ? fake_set_timeout
          : setTimeout;

      const step = test_this.step_func((result) => {
        if (result) {
          func();
        } else {
          if (remaining === 0) {
            assert(
              false,
              "step_wait_func",
              description,
              "Timed out waiting on condition"
            );
          }
          remaining--;
          local_set_timeout(wait_for_inner, interval);
        }
      });

      var wait_for_inner = test_this.step_func(() => {
        Promise.resolve(cond()).then(
          step,
          test_this.unreached_func("step_wait_func")
        );
      });

      wait_for_inner();
    };

    /**
     * Poll for a function to return true, and invoke a callback
     * followed by this.done() once it does, or assert if a timeout
     * is reached. This is preferred over a simple step_timeout
     * whenever possible since it allows the timeout to be longer
     * to reduce intermittents without compromising test execution speed
     * when the condition is quickly met.
     *
     * @example
     * async_test(t => {
     *  const popup = window.open("resources/coop-coep.py?coop=same-origin&coep=&navigate=about:blank");
     *  t.add_cleanup(() => popup.close());
     *  assert_equals(window, popup.opener);
     *
     *  popup.onload = t.step_func(() => {
     *    assert_true(popup.location.href.endsWith("&navigate=about:blank"));
     *    // Use step_wait_func_done as about:blank cannot message back.
     *    t.step_wait_func_done(() => popup.location.href === "about:blank");
     *  });
     * }, "Navigating a popup to about:blank");
     *
     * @param {Function} cond A function taking no arguments and
     *                        returning a boolean or a Promise. The callback is
     *                        called when this function returns true, or the
     *                        returned Promise is resolved with true.
     * @param {Function} func A function taking no arguments to call once
     *                        the condition is met.
     * @param {string} [description] Error message to add to assert in case of
     *                               failure.
     * @param {number} timeout Timeout in ms. This is multiplied by the global
     *                         timeout_multiplier
     * @param {number} interval Polling interval in ms
     *
     */
    Test.prototype.step_wait_func_done = function (
      cond,
      func,
      description,
      timeout = 3000,
      interval = 100
    ) {
      this.step_wait_func(
        cond,
        () => {
          if (func) {
            func();
          }
          this.done();
        },
        description,
        timeout,
        interval
      );
    };

    /**
     * Poll for a function to return true, and resolve a promise
     * once it does, or assert if a timeout is reached. This is
     * preferred over a simple step_timeout whenever possible
     * since it allows the timeout to be longer to reduce
     * intermittents without compromising test execution speed
     * when the condition is quickly met.
     *
     * @example
     * promise_test(async t => {
     *  // …
     * await t.step_wait(() => frame.contentDocument === null, "Frame navigated to a cross-origin document");
     * // …
     * }, "");
     *
     * @param {Function} cond A function taking no arguments and
     *                        returning a boolean or a Promise.
     * @param {string} [description] Error message to add to assert in case of
     *                              failure.
     * @param {number} timeout Timeout in ms. This is multiplied by the global
     *                         timeout_multiplier
     * @param {number} interval Polling interval in ms
     * @returns {Promise} Promise resolved once cond is met.
     *
     */
    Test.prototype.step_wait = function (
      cond,
      description,
      timeout = 3000,
      interval = 100
    ) {
      return new Promise((resolve) => {
        this.step_wait_func(cond, resolve, description, timeout, interval);
      });
    };

    /*
     * Private method for registering cleanup functions. `testharness.js`
     * internals should use this method instead of the public `add_cleanup`
     * method in order to hide implementation details from the harness status
     * message in the case errors.
     */
    Test.prototype._add_cleanup = function (callback) {
      this.cleanup_callbacks.push(callback);
    };

    /**
     * Schedule a function to be run after the test result is known, regardless
     * of passing or failing state.
     *
     * The behavior of this function will not
     * influence the result of the test, but if an exception is thrown, the
     * test harness will report an error.
     *
     * @param {Function} callback - The cleanup function to run. This
     * is called with no arguments.
     */
    Test.prototype.add_cleanup = function (callback) {
      this._user_defined_cleanup_count += 1;
      this._add_cleanup(callback);
    };

    Test.prototype.set_timeout = function () {
      if (this.timeout_length !== null) {
        var this_obj = this;
        this.timeout_id = setTimeout(function () {
          this_obj.timeout();
        }, this.timeout_length);
      }
    };

    Test.prototype.set_status = function (status, message, stack) {
      this.status = status;
      this.message = message;
      this.stack = stack ? stack : null;
    };

    /**
     * Manually set the test status to ``TIMEOUT``.
     */
    Test.prototype.timeout = function () {
      this.timeout_id = null;
      this.set_status(this.TIMEOUT, "Test timed out");
      this.phase = this.phases.HAS_RESULT;
      this.done();
    };

    /**
     * Manually set the test status to ``TIMEOUT``.
     *
     * Alias for `Test.timeout <#Test.timeout>`_.
     */
    Test.prototype.force_timeout = function () {
      return this.timeout();
    };

    /**
     * Mark the test as complete.
     *
     * This sets the test status to ``PASS`` if no other status was
     * already recorded. Any subsequent attempts to run additional
     * test steps will be ignored.
     *
     * After setting the test status any test cleanup functions will
     * be run.
     */
    Test.prototype.done = function () {
      if (this.phase >= this.phases.CLEANING) {
        return;
      }

      if (this.phase <= this.phases.STARTED) {
        this.set_status(this.PASS, null);
      }

      if (global_scope.clearTimeout) {
        clearTimeout(this.timeout_id);
      }

      if (settings.debug) {
        console.log("TEST DONE", this.status, this.name);
      }

      this.cleanup();
    };

    function add_test_done_callback(test, callback) {
      if (test.phase === test.phases.COMPLETE) {
        callback();
        return;
      }

      test._done_callbacks.push(callback);
    }

    /*
     * Invoke all specified cleanup functions. If one or more produce an error,
     * the context is in an unpredictable state, so all further testing should
     * be cancelled.
     */
    Test.prototype.cleanup = function () {
      var errors = [];
      var bad_value_count = 0;
      function on_error(e) {
        errors.push(e);
        // Abort tests immediately so that tests declared within subsequent
        // cleanup functions are not run.
        tests.abort();
      }
      var this_obj = this;
      var results = [];

      this.phase = this.phases.CLEANING;

      if (this._abortController) {
        this._abortController.abort("Test cleanup");
      }

      forEach(this.cleanup_callbacks, function (cleanup_callback) {
        var result;

        try {
          result = cleanup_callback();
        } catch (e) {
          on_error(e);
          return;
        }

        if (!is_valid_cleanup_result(this_obj, result)) {
          bad_value_count += 1;
          // Abort tests immediately so that tests declared
          // within subsequent cleanup functions are not run.
          tests.abort();
        }

        results.push(result);
      });

      if (!this._is_promise_test) {
        cleanup_done(this_obj, errors, bad_value_count);
      } else {
        all_async(
          results,
          function (result, done) {
            if (result && typeof result.then === "function") {
              result.then(null, on_error).then(done);
            } else {
              done();
            }
          },
          function () {
            cleanup_done(this_obj, errors, bad_value_count);
          }
        );
      }
    };

    /*
     * Determine if the return value of a cleanup function is valid for a given
     * test. Any test may return the value `undefined`. Tests created with
     * `promise_test` may alternatively return "thenable" object values.
     */
    function is_valid_cleanup_result(test, result) {
      if (result === undefined) {
        return true;
      }

      if (test._is_promise_test) {
        return result && typeof result.then === "function";
      }

      return false;
    }

    function cleanup_done(test, errors, bad_value_count) {
      if (errors.length || bad_value_count) {
        var total = test._user_defined_cleanup_count;

        tests.status.status = tests.status.ERROR;
        tests.status.stack = null;
        tests.status.message =
          "Test named '" +
          test.name +
          "' specified " +
          total +
          " 'cleanup' function" +
          (total > 1 ? "s" : "");

        if (errors.length) {
          tests.status.message += ", and " + errors.length + " failed";
          tests.status.stack =
            typeof errors[0] === "object" && errors[0].hasOwnProperty("stack")
              ? errors[0].stack
              : null;
        }

        if (bad_value_count) {
          var type = test._is_promise_test ? "non-thenable" : "non-undefined";
          tests.status.message +=
            ", and " + bad_value_count + " returned a " + type + " value";
        }

        tests.status.message += ".";
      }

      test.phase = test.phases.COMPLETE;
      tests.result(test);
      forEach(test._done_callbacks, function (callback) {
        callback();
      });
      test._done_callbacks.length = 0;
    }

    /**
     * Gives an AbortSignal that will be aborted when the test finishes.
     */
    Test.prototype.get_signal = function () {
      if (!this._abortController) {
        throw new Error("AbortController is not supported in this browser");
      }
      return this._abortController.signal;
    };

    /**
     * A RemoteTest object mirrors a Test object on a remote worker. The
     * associated RemoteWorker updates the RemoteTest object in response to
     * received events. In turn, the RemoteTest object replicates these events
     * on the local document. This allows listeners (test result reporting
     * etc..) to transparently handle local and remote events.
     */
    function RemoteTest(clone) {
      var this_obj = this;
      Object.keys(clone).forEach(function (key) {
        this_obj[key] = clone[key];
      });
      this.index = null;
      this.phase = this.phases.INITIAL;
      this.update_state_from(clone);
      this._done_callbacks = [];
      tests.push(this);
    }

    RemoteTest.prototype.structured_clone = function () {
      var clone = {};
      Object.keys(this).forEach(
        function (key) {
          var value = this[key];
          // `RemoteTest` instances are responsible for managing
          // their own "done" callback functions, so those functions
          // are not relevant in other execution contexts. Because of
          // this (and because Function values cannot be serialized
          // for cross-realm transmittance), the property should not
          // be considered when cloning instances.
          if (key === "_done_callbacks") {
            return;
          }

          if (typeof value === "object" && value !== null) {
            clone[key] = merge({}, value);
          } else {
            clone[key] = value;
          }
        }.bind(this)
      );
      clone.phases = merge({}, this.phases);
      return clone;
    };

    /**
     * `RemoteTest` instances are objects which represent tests running in
     * another realm. They do not define "cleanup" functions (if necessary,
     * such functions are defined on the associated `Test` instance within the
     * external realm). However, `RemoteTests` may have "done" callbacks (e.g.
     * as attached by the `Tests` instance responsible for tracking the overall
     * test status in the parent realm). The `cleanup` method delegates to
     * `done` in order to ensure that such callbacks are invoked following the
     * completion of the `RemoteTest`.
     */
    RemoteTest.prototype.cleanup = function () {
      this.done();
    };
    RemoteTest.prototype.phases = Test.prototype.phases;
    RemoteTest.prototype.update_state_from = function (clone) {
      this.status = clone.status;
      this.message = clone.message;
      this.stack = clone.stack;
      if (this.phase === this.phases.INITIAL) {
        this.phase = this.phases.STARTED;
      }
    };
    RemoteTest.prototype.done = function () {
      this.phase = this.phases.COMPLETE;

      forEach(this._done_callbacks, function (callback) {
        callback();
      });
    };

    RemoteTest.prototype.format_status = function () {
      return Test.prototype.status_formats[this.status];
    };

    /*
     * A RemoteContext listens for test events from a remote test context, such
     * as another window or a worker. These events are then used to construct
     * and maintain RemoteTest objects that mirror the tests running in the
     * remote context.
     *
     * An optional third parameter can be used as a predicate to filter incoming
     * MessageEvents.
     */
    function RemoteContext(remote, message_target, message_filter) {
      this.running = true;
      this.started = false;
      this.tests = new Array();
      this.early_exception = null;

      var this_obj = this;
      // If remote context is cross origin assigning to onerror is not
      // possible, so silently catch those errors.
      try {
        remote.onerror = function (error) {
          this_obj.remote_error(error);
        };
      } catch (e) {
        // Ignore.
      }

      // Keeping a reference to the remote object and the message handler until
      // remote_done() is seen prevents the remote object and its message channel
      // from going away before all the messages are dispatched.
      this.remote = remote;
      this.message_target = message_target;
      this.message_handler = function (message) {
        var passesFilter = !message_filter || message_filter(message);
        // The reference to the `running` property in the following
        // condition is unnecessary because that value is only set to
        // `false` after the `message_handler` function has been
        // unsubscribed.
        // TODO: Simplify the condition by removing the reference.
        if (
          this_obj.running &&
          message.data &&
          passesFilter &&
          message.data.type in this_obj.message_handlers
        ) {
          this_obj.message_handlers[message.data.type].call(
            this_obj,
            message.data
          );
        }
      };

      if (self.Promise) {
        this.done = new Promise(function (resolve) {
          this_obj.doneResolve = resolve;
        });
      }

      this.message_target.addEventListener("message", this.message_handler);
    }

    RemoteContext.prototype.remote_error = function (error) {
      if (error.preventDefault) {
        error.preventDefault();
      }

      // Defer interpretation of errors until the testing protocol has
      // started and the remote test's `allow_uncaught_exception` property
      // is available.
      if (!this.started) {
        this.early_exception = error;
      } else if (!this.allow_uncaught_exception) {
        this.report_uncaught(error);
      }
    };

    RemoteContext.prototype.report_uncaught = function (error) {
      var message = error.message || String(error);
      var filename = error.filename ? " " + error.filename : "";
      // FIXME: Display remote error states separately from main document
      // error state.
      tests.set_status(
        tests.status.ERROR,
        "Error in remote" + filename + ": " + message,
        error.stack
      );
    };

    RemoteContext.prototype.start = function (data) {
      this.started = true;
      this.allow_uncaught_exception = data.properties.allow_uncaught_exception;

      if (this.early_exception && !this.allow_uncaught_exception) {
        this.report_uncaught(this.early_exception);
      }
    };

    RemoteContext.prototype.test_state = function (data) {
      var remote_test = this.tests[data.test.index];
      if (!remote_test) {
        remote_test = new RemoteTest(data.test);
        this.tests[data.test.index] = remote_test;
      }
      remote_test.update_state_from(data.test);
      tests.notify_test_state(remote_test);
    };

    RemoteContext.prototype.test_done = function (data) {
      var remote_test = this.tests[data.test.index];
      remote_test.update_state_from(data.test);
      remote_test.done();
      tests.result(remote_test);
    };

    RemoteContext.prototype.remote_done = function (data) {
      if (
        tests.status.status === null &&
        data.status.status !== data.status.OK
      ) {
        tests.set_status(
          data.status.status,
          data.status.message,
          data.status.stack
        );
      }

      for (let assert of data.asserts) {
        var record = new AssertRecord();
        record.assert_name = assert.assert_name;
        record.args = assert.args;
        record.test =
          assert.test != null ? this.tests[assert.test.index] : null;
        record.status = assert.status;
        record.stack = assert.stack;
        tests.asserts_run.push(record);
      }

      this.message_target.removeEventListener("message", this.message_handler);
      this.running = false;

      // If remote context is cross origin assigning to onerror is not
      // possible, so silently catch those errors.
      try {
        this.remote.onerror = null;
      } catch (e) {
        // Ignore.
      }

      this.remote = null;
      this.message_target = null;
      if (this.doneResolve) {
        this.doneResolve();
      }

      if (tests.all_done()) {
        tests.complete();
      }
    };

    RemoteContext.prototype.message_handlers = {
      start: RemoteContext.prototype.start,
      test_state: RemoteContext.prototype.test_state,
      result: RemoteContext.prototype.test_done,
      complete: RemoteContext.prototype.remote_done,
    };

    /**
     * @class
     * Status of the overall harness
     */
    function TestsStatus() {
      /** The status code */
      this.status = null;
      /** Message in case of failure */
      this.message = null;
      /** Stack trace in case of an exception. */
      this.stack = null;
    }

    /**
     * Enum of possible harness statuses.
     *
     * :values:
     *   - ``OK``
     *   - ``ERROR``
     *   - ``TIMEOUT``
     *   - ``PRECONDITION_FAILED``
     */
    TestsStatus.statuses = {
      OK: 0,
      ERROR: 1,
      TIMEOUT: 2,
      PRECONDITION_FAILED: 3,
    };

    TestsStatus.prototype = merge({}, TestsStatus.statuses);

    TestsStatus.prototype.formats = {
      0: "OK",
      1: "Error",
      2: "Timeout",
      3: "Optional Feature Unsupported",
    };

    TestsStatus.prototype.structured_clone = function () {
      if (!this._structured_clone) {
        var msg = this.message;
        msg = msg ? String(msg) : msg;
        this._structured_clone = merge(
          {
            status: this.status,
            message: msg,
            stack: this.stack,
          },
          TestsStatus.statuses
        );
      }
      return this._structured_clone;
    };

    TestsStatus.prototype.format_status = function () {
      return this.formats[this.status];
    };

    /**
     * @class
     * Record of an assert that ran.
     *
     * @param {Test} test - The test which ran the assert.
     * @param {string} assert_name - The function name of the assert.
     * @param {Any} args - The arguments passed to the assert function.
     */
    function AssertRecord(test, assert_name, args = []) {
      /** Name of the assert that ran */
      this.assert_name = assert_name;
      /** Test that ran the assert */
      this.test = test;
      // Avoid keeping complex objects alive
      /** Stringification of the arguments that were passed to the assert function */
      this.args = args.map((x) => format_value(x).replace(/\n/g, " "));
      /** Status of the assert */
      this.status = null;
    }

    AssertRecord.prototype.structured_clone = function () {
      return {
        assert_name: this.assert_name,
        test: this.test ? this.test.structured_clone() : null,
        args: this.args,
        status: this.status,
      };
    };

    function Tests() {
      this.tests = [];
      this.num_pending = 0;

      this.phases = {
        INITIAL: 0,
        SETUP: 1,
        HAVE_TESTS: 2,
        HAVE_RESULTS: 3,
        COMPLETE: 4,
      };
      this.phase = this.phases.INITIAL;

      this.properties = {};

      this.wait_for_finish = false;
      this.processing_callbacks = false;

      this.allow_uncaught_exception = false;

      this.file_is_test = false;
      // This value is lazily initialized in order to avoid introducing a
      // dependency on ECMAScript 2015 Promises to all tests.
      this.promise_tests = null;
      this.promise_setup_called = false;

      this.timeout_multiplier = 1;
      this.timeout_length = test_environment.test_timeout();
      this.timeout_id = null;

      this.start_callbacks = [];
      this.test_state_callbacks = [];
      this.test_done_callbacks = [];
      this.all_done_callbacks = [];

      this.hide_test_state = false;
      this.pending_remotes = [];

      this.current_test = null;
      this.asserts_run = [];

      // Track whether output is enabled, and thus whether or not we should
      // track asserts.
      //
      // On workers we don't get properties set from testharnessreport.js, so
      // we don't know whether or not to track asserts. To avoid the
      // resulting performance hit, we assume we are not meant to. This means
      // that assert tracking does not function on workers.
      this.output = settings.output && "document" in global_scope;

      this.status = new TestsStatus();

      var this_obj = this;

      test_environment.add_on_loaded_callback(function () {
        if (this_obj.all_done()) {
          this_obj.complete();
        }
      });

      this.set_timeout();
    }

    Tests.prototype.setup = function (func, properties) {
      if (this.phase >= this.phases.HAVE_RESULTS) {
        return;
      }

      if (this.phase < this.phases.SETUP) {
        this.phase = this.phases.SETUP;
      }

      this.properties = properties;

      for (var p in properties) {
        if (properties.hasOwnProperty(p)) {
          var value = properties[p];
          if (p == "allow_uncaught_exception") {
            this.allow_uncaught_exception = value;
          } else if (p == "explicit_done" && value) {
            this.wait_for_finish = true;
          } else if (p == "explicit_timeout" && value) {
            this.timeout_length = null;
            if (this.timeout_id) {
              clearTimeout(this.timeout_id);
            }
          } else if (p == "single_test" && value) {
            this.set_file_is_test();
          } else if (p == "timeout_multiplier") {
            this.timeout_multiplier = value;
            if (this.timeout_length) {
              this.timeout_length *= this.timeout_multiplier;
            }
          } else if (p == "hide_test_state") {
            this.hide_test_state = value;
          } else if (p == "output") {
            this.output = value;
          } else if (p === "debug") {
            settings.debug = value;
          }
        }
      }

      if (func) {
        try {
          func();
        } catch (e) {
          this.status.status =
            e instanceof OptionalFeatureUnsupportedError
              ? this.status.PRECONDITION_FAILED
              : this.status.ERROR;
          this.status.message = String(e);
          this.status.stack = e.stack ? e.stack : null;
          this.complete();
        }
      }
      this.set_timeout();
    };

    Tests.prototype.set_file_is_test = function () {
      if (this.tests.length > 0) {
        throw new Error("Tried to set file as test after creating a test");
      }
      this.wait_for_finish = true;
      this.file_is_test = true;
      // Create the test, which will add it to the list of tests
      tests.current_test = async_test();
    };

    Tests.prototype.set_status = function (status, message, stack) {
      this.status.status = status;
      this.status.message = message;
      this.status.stack = stack ? stack : null;
    };

    Tests.prototype.set_timeout = function () {
      if (global_scope.clearTimeout) {
        var this_obj = this;
        clearTimeout(this.timeout_id);
        if (this.timeout_length !== null) {
          this.timeout_id = setTimeout(function () {
            this_obj.timeout();
          }, this.timeout_length);
        }
      }
    };

    Tests.prototype.timeout = function () {
      var test_in_cleanup = null;

      if (this.status.status === null) {
        forEach(this.tests, function (test) {
          // No more than one test is expected to be in the
          // "CLEANUP" phase at any time
          if (test.phase === test.phases.CLEANING) {
            test_in_cleanup = test;
          }

          test.phase = test.phases.COMPLETE;
        });

        // Timeouts that occur while a test is in the "cleanup" phase
        // indicate that some global state was not properly reverted. This
        // invalidates the overall test execution, so the timeout should be
        // reported as an error and cancel the execution of any remaining
        // tests.
        if (test_in_cleanup) {
          this.status.status = this.status.ERROR;
          this.status.message =
            "Timeout while running cleanup for " +
            'test named "' +
            test_in_cleanup.name +
            '".';
          tests.status.stack = null;
        } else {
          this.status.status = this.status.TIMEOUT;
        }
      }

      this.complete();
    };

    Tests.prototype.end_wait = function () {
      this.wait_for_finish = false;
      if (this.all_done()) {
        this.complete();
      }
    };

    Tests.prototype.push = function (test) {
      if (this.phase < this.phases.HAVE_TESTS) {
        this.start();
      }
      this.num_pending++;
      test.index = this.tests.push(test);
      this.notify_test_state(test);
    };

    Tests.prototype.notify_test_state = function (test) {
      var this_obj = this;
      forEach(this.test_state_callbacks, function (callback) {
        callback(test, this_obj);
      });
    };

    Tests.prototype.all_done = function () {
      return (
        (this.tests.length > 0 || this.pending_remotes.length > 0) &&
        test_environment.all_loaded &&
        (this.num_pending === 0 || this.is_aborted) &&
        !this.wait_for_finish &&
        !this.processing_callbacks &&
        !this.pending_remotes.some(function (w) {
          return w.running;
        })
      );
    };

    Tests.prototype.start = function () {
      this.phase = this.phases.HAVE_TESTS;
      this.notify_start();
    };

    Tests.prototype.notify_start = function () {
      var this_obj = this;
      forEach(this.start_callbacks, function (callback) {
        callback(this_obj.properties);
      });
    };

    Tests.prototype.result = function (test) {
      // If the harness has already transitioned beyond the `HAVE_RESULTS`
      // phase, subsequent tests should not cause it to revert.
      if (this.phase <= this.phases.HAVE_RESULTS) {
        this.phase = this.phases.HAVE_RESULTS;
      }
      this.num_pending--;
      this.notify_result(test);
    };

    Tests.prototype.notify_result = function (test) {
      var this_obj = this;
      this.processing_callbacks = true;
      forEach(this.test_done_callbacks, function (callback) {
        callback(test, this_obj);
      });
      this.processing_callbacks = false;
      if (this_obj.all_done()) {
        this_obj.complete();
      }
    };

    Tests.prototype.complete = function () {
      if (this.phase === this.phases.COMPLETE) {
        return;
      }
      var this_obj = this;
      var all_complete = function () {
        this_obj.phase = this_obj.phases.COMPLETE;
        this_obj.notify_complete();
      };
      var incomplete = filter(this.tests, function (test) {
        return test.phase < test.phases.COMPLETE;
      });

      /**
       * To preserve legacy behavior, overall test completion must be
       * signaled synchronously.
       */
      if (incomplete.length === 0) {
        all_complete();
        return;
      }

      all_async(
        incomplete,
        function (test, testDone) {
          if (test.phase === test.phases.INITIAL) {
            test.phase = test.phases.COMPLETE;
            testDone();
          } else {
            add_test_done_callback(test, testDone);
            test.cleanup();
          }
        },
        all_complete
      );
    };

    Tests.prototype.set_assert = function (assert_name, args) {
      this.asserts_run.push(
        new AssertRecord(this.current_test, assert_name, args)
      );
    };

    Tests.prototype.set_assert_status = function (index, status, stack) {
      let assert_record = this.asserts_run[index];
      assert_record.status = status;
      assert_record.stack = stack;
    };

    /**
     * Update the harness status to reflect an unrecoverable harness error that
     * should cancel all further testing. Update all previously-defined tests
     * which have not yet started to indicate that they will not be executed.
     */
    Tests.prototype.abort = function () {
      this.status.status = this.status.ERROR;
      this.is_aborted = true;

      forEach(this.tests, function (test) {
        if (test.phase === test.phases.INITIAL) {
          test.phase = test.phases.COMPLETE;
        }
      });
    };

    /*
     * Determine if any tests share the same `name` property. Return an array
     * containing the names of any such duplicates.
     */
    Tests.prototype.find_duplicates = function () {
      var names = Object.create(null);
      var duplicates = [];

      forEach(this.tests, function (test) {
        if (test.name in names && duplicates.indexOf(test.name) === -1) {
          duplicates.push(test.name);
        }
        names[test.name] = true;
      });

      return duplicates;
    };

    function code_unit_str(char) {
      return "U+" + char.charCodeAt(0).toString(16);
    }

    function sanitize_unpaired_surrogates(str) {
      return str.replace(
        /([\ud800-\udbff]+)(?![\udc00-\udfff])|(^|[^\ud800-\udbff])([\udc00-\udfff]+)/g,
        function (_, low, prefix, high) {
          var output = prefix || ""; // prefix may be undefined
          var string = low || high; // only one of these alternates can match
          for (var i = 0; i < string.length; i++) {
            output += code_unit_str(string[i]);
          }
          return output;
        }
      );
    }

    function sanitize_all_unpaired_surrogates(tests) {
      forEach(tests, function (test) {
        var sanitized = sanitize_unpaired_surrogates(test.name);

        if (test.name !== sanitized) {
          test.name = sanitized;
          delete test._structured_clone;
        }
      });
    }

    Tests.prototype.notify_complete = function () {
      var this_obj = this;
      var duplicates;

      if (this.status.status === null) {
        duplicates = this.find_duplicates();

        // Some transports adhere to UTF-8's restriction on unpaired
        // surrogates. Sanitize the titles so that the results can be
        // consistently sent via all transports.
        sanitize_all_unpaired_surrogates(this.tests);

        // Test names are presumed to be unique within test files--this
        // allows consumers to use them for identification purposes.
        // Duplicated names violate this expectation and should therefore
        // be reported as an error.
        if (duplicates.length) {
          this.status.status = this.status.ERROR;
          this.status.message =
            duplicates.length +
            " duplicate test name" +
            (duplicates.length > 1 ? "s" : "") +
            ': "' +
            duplicates.join('", "') +
            '"';
        } else {
          this.status.status = this.status.OK;
        }
      }

      forEach(this.all_done_callbacks, function (callback) {
        callback(this_obj.tests, this_obj.status, this_obj.asserts_run);
      });
    };

    /*
     * Constructs a RemoteContext that tracks tests from a specific worker.
     */
    Tests.prototype.create_remote_worker = function (worker) {
      var message_port;

      if (is_service_worker(worker)) {
        message_port = navigator.serviceWorker;
        worker.postMessage({ type: "connect" });
      } else if (is_shared_worker(worker)) {
        message_port = worker.port;
        message_port.start();
      } else {
        message_port = worker;
      }

      return new RemoteContext(worker, message_port);
    };

    /*
     * Constructs a RemoteContext that tracks tests from a specific window.
     */
    Tests.prototype.create_remote_window = function (remote) {
      remote.postMessage({ type: "getmessages" }, "*");
      return new RemoteContext(remote, window, function (msg) {
        return msg.source === remote;
      });
    };

    Tests.prototype.fetch_tests_from_worker = function (worker) {
      if (this.phase >= this.phases.COMPLETE) {
        return;
      }

      var remoteContext = this.create_remote_worker(worker);
      this.pending_remotes.push(remoteContext);
      return remoteContext.done;
    };

    /**
     * Get test results from a worker and include them in the current test.
     *
     * @param {Worker|SharedWorker|ServiceWorker|MessagePort} port -
     * Either a worker object or a port connected to a worker which is
     * running tests..
     * @returns {Promise} - A promise that's resolved once all the remote tests are complete.
     */
    function fetch_tests_from_worker(port) {
      return tests.fetch_tests_from_worker(port);
    }
    expose(fetch_tests_from_worker, "fetch_tests_from_worker");

    Tests.prototype.fetch_tests_from_window = function (remote) {
      if (this.phase >= this.phases.COMPLETE) {
        return;
      }

      var remoteContext = this.create_remote_window(remote);
      this.pending_remotes.push(remoteContext);
      return remoteContext.done;
    };

    /**
     * Aggregate tests from separate windows or iframes
     * into the current document as if they were all part of the same test file.
     *
     * The document of the second window (or iframe) should include
     * ``testharness.js``, but not ``testharnessreport.js``, and use
     * :js:func:`test`, :js:func:`async_test`, and :js:func:`promise_test` in
     * the usual manner.
     *
     * @param {Window} window - The window to fetch tests from.
     */
    function fetch_tests_from_window(window) {
      return tests.fetch_tests_from_window(window);
    }
    expose(fetch_tests_from_window, "fetch_tests_from_window");

    /**
     * Get test results from a shadow realm and include them in the current test.
     *
     * @param {ShadowRealm} realm - A shadow realm also running the test harness
     * @returns {Promise} - A promise that's resolved once all the remote tests are complete.
     */
    function fetch_tests_from_shadow_realm(realm) {
      var chan = new MessageChannel();
      function receiveMessage(msg_json) {
        chan.port1.postMessage(JSON.parse(msg_json));
      }
      var done = tests.fetch_tests_from_worker(chan.port2);
      realm.evaluate("begin_shadow_realm_tests")(receiveMessage);
      chan.port2.start();
      return done;
    }
    expose(fetch_tests_from_shadow_realm, "fetch_tests_from_shadow_realm");

    /**
     * Begin running tests in this shadow realm test harness.
     *
     * To be called after all tests have been loaded; it is an error to call
     * this more than once or in a non-Shadow Realm environment
     *
     * @param {Function} postMessage - A function to send test updates to the
     * incubating realm-- accepts JSON-encoded messages in the format used by
     * RemoteContext
     */
    function begin_shadow_realm_tests(postMessage) {
      if (!(test_environment instanceof ShadowRealmTestEnvironment)) {
        throw new Error(
          "begin_shadow_realm_tests called in non-Shadow Realm environment"
        );
      }

      test_environment.begin(function (msg) {
        postMessage(JSON.stringify(msg));
      });
    }
    expose(begin_shadow_realm_tests, "begin_shadow_realm_tests");

    /**
     * Timeout the tests.
     *
     * This only has an effect when ``explicit_timeout`` has been set
     * in :js:func:`setup`. In other cases any call is a no-op.
     *
     */
    function timeout() {
      if (tests.timeout_length === null) {
        tests.timeout();
      }
    }
    expose(timeout, "timeout");

    /**
     * Add a callback that's triggered when the first :js:class:`Test` is created.
     *
     * @param {Function} callback - Callback function. This is called
     * without arguments.
     */
    function add_start_callback(callback) {
      tests.start_callbacks.push(callback);
    }

    /**
     * Add a callback that's triggered when a test state changes.
     *
     * @param {Function} callback - Callback function, called with the
     * :js:class:`Test` as the only argument.
     */
    function add_test_state_callback(callback) {
      tests.test_state_callbacks.push(callback);
    }

    /**
     * Add a callback that's triggered when a test result is received.
     *
     * @param {Function} callback - Callback function, called with the
     * :js:class:`Test` as the only argument.
     */
    function add_result_callback(callback) {
      tests.test_done_callbacks.push(callback);
    }

    /**
     * Add a callback that's triggered when all tests are complete.
     *
     * @param {Function} callback - Callback function, called with an
     * array of :js:class:`Test` objects, a :js:class:`TestsStatus`
     * object and an array of :js:class:`AssertRecord` objects. If the
     * debug setting is ``false`` the final argument will be an empty
     * array.
     *
     * For performance reasons asserts are only tracked when the debug
     * setting is ``true``. In other cases the array of asserts will be
     * empty.
     */
    function add_completion_callback(callback) {
      tests.all_done_callbacks.push(callback);
    }

    expose(add_start_callback, "add_start_callback");
    expose(add_test_state_callback, "add_test_state_callback");
    expose(add_result_callback, "add_result_callback");
    expose(add_completion_callback, "add_completion_callback");

    function remove(array, item) {
      var index = array.indexOf(item);
      if (index > -1) {
        array.splice(index, 1);
      }
    }

    function remove_start_callback(callback) {
      remove(tests.start_callbacks, callback);
    }

    function remove_test_state_callback(callback) {
      remove(tests.test_state_callbacks, callback);
    }

    function remove_result_callback(callback) {
      remove(tests.test_done_callbacks, callback);
    }

    function remove_completion_callback(callback) {
      remove(tests.all_done_callbacks, callback);
    }

    /*
     * Output listener
     */

    function Output() {
      this.output_document = document;
      this.output_node = null;
      this.enabled = settings.output;
      this.phase = this.INITIAL;
    }

    Output.prototype.INITIAL = 0;
    Output.prototype.STARTED = 1;
    Output.prototype.HAVE_RESULTS = 2;
    Output.prototype.COMPLETE = 3;

    Output.prototype.setup = function (properties) {
      if (this.phase > this.INITIAL) {
        return;
      }

      //If output is disabled in testharnessreport.js the test shouldn't be
      //able to override that
      this.enabled =
        this.enabled &&
        (properties.hasOwnProperty("output")
          ? properties.output
          : settings.output);
    };

    Output.prototype.init = function (properties) {
      if (this.phase >= this.STARTED) {
        return;
      }
      if (properties.output_document) {
        this.output_document = properties.output_document;
      } else {
        this.output_document = document;
      }
      this.phase = this.STARTED;
    };

    Output.prototype.resolve_log = function () {
      var output_document;
      if (this.output_node) {
        return;
      }
      if (typeof this.output_document === "function") {
        output_document = this.output_document.apply(undefined);
      } else {
        output_document = this.output_document;
      }
      if (!output_document) {
        return;
      }
      var node = output_document.getElementById("log");
      if (!node) {
        if (output_document.readyState === "loading") {
          return;
        }
        node = output_document.createElementNS(
          "http://www.w3.org/1999/xhtml",
          "div"
        );
        node.id = "log";
        if (output_document.body) {
          output_document.body.appendChild(node);
        } else {
          var root = output_document.documentElement;
          var is_html =
            root &&
            root.namespaceURI == "http://www.w3.org/1999/xhtml" &&
            root.localName == "html";
          var is_svg =
            output_document.defaultView &&
            "SVGSVGElement" in output_document.defaultView &&
            root instanceof output_document.defaultView.SVGSVGElement;
          if (is_svg) {
            var foreignObject = output_document.createElementNS(
              "http://www.w3.org/2000/svg",
              "foreignObject"
            );
            foreignObject.setAttribute("width", "100%");
            foreignObject.setAttribute("height", "100%");
            root.appendChild(foreignObject);
            foreignObject.appendChild(node);
          } else if (is_html) {
            root
              .appendChild(
                output_document.createElementNS(
                  "http://www.w3.org/1999/xhtml",
                  "body"
                )
              )
              .appendChild(node);
          } else {
            root.appendChild(node);
          }
        }
      }
      this.output_document = output_document;
      this.output_node = node;
    };

    Output.prototype.show_status = function () {
      if (this.phase < this.STARTED) {
        this.init({});
      }
      if (!this.enabled || this.phase === this.COMPLETE) {
        return;
      }
      this.resolve_log();
      if (this.phase < this.HAVE_RESULTS) {
        this.phase = this.HAVE_RESULTS;
      }
      var done_count = tests.tests.length - tests.num_pending;
      if (this.output_node && !tests.hide_test_state) {
        if (
          done_count < 100 ||
          (done_count < 1000 && done_count % 100 === 0) ||
          done_count % 1000 === 0
        ) {
          this.output_node.textContent =
            "Running, " +
            done_count +
            " complete, " +
            tests.num_pending +
            " remain";
        }
      }
    };

    Output.prototype.show_results = function (
      tests,
      harness_status,
      asserts_run
    ) {
      if (this.phase >= this.COMPLETE) {
        return;
      }
      if (!this.enabled) {
        return;
      }
      if (!this.output_node) {
        this.resolve_log();
      }
      this.phase = this.COMPLETE;

      var log = this.output_node;
      if (!log) {
        return;
      }
      var output_document = this.output_document;

      while (log.lastChild) {
        log.removeChild(log.lastChild);
      }

      var stylesheet = output_document.createElementNS(xhtml_ns, "style");
      stylesheet.textContent = stylesheetContent;
      var heads = output_document.getElementsByTagName("head");
      if (heads.length) {
        heads[0].appendChild(stylesheet);
      }

      var status_number = {};
      forEach(tests, function (test) {
        var status = test.format_status();
        if (status_number.hasOwnProperty(status)) {
          status_number[status] += 1;
        } else {
          status_number[status] = 1;
        }
      });

      function status_class(status) {
        return status.replace(/\s/g, "").toLowerCase();
      }

      var summary_template = [
        "section",
        { id: "summary" },
        ["h2", {}, "Summary"],
        function () {
          var status = harness_status.format_status();
          var rv = [
            [
              "section",
              {},
              [
                "p",
                {},
                "Harness status: ",
                ["span", { class: status_class(status) }, status],
              ],
              ["button", { id: "rerun" }, "Rerun"],
            ],
          ];

          if (harness_status.status === harness_status.ERROR) {
            rv[0].push(["pre", {}, harness_status.message]);
            if (harness_status.stack) {
              rv[0].push(["pre", {}, harness_status.stack]);
            }
          }
          return rv;
        },
        ["p", {}, "Found ${num_tests} tests"],
        function () {
          var rv = [["div", {}]];
          var i = 0;
          while (Test.prototype.status_formats.hasOwnProperty(i)) {
            if (
              status_number.hasOwnProperty(Test.prototype.status_formats[i])
            ) {
              var status = Test.prototype.status_formats[i];
              rv[0].push([
                "div",
                {},
                [
                  "label",
                  {},
                  ["input", { type: "checkbox", checked: "checked" }],
                  status_number[status] + " ",
                  ["span", { class: status_class(status) }, status],
                ],
              ]);
            }
            i++;
          }
          return rv;
        },
      ];

      log.appendChild(
        render(summary_template, { num_tests: tests.length }, output_document)
      );

      output_document
        .getElementById("rerun")
        .addEventListener("click", function () {
          let evt = new Event("__test_restart");
          let canceled = !window.dispatchEvent(evt);
          if (!canceled) {
            location.reload();
          }
        });

      forEach(
        output_document.querySelectorAll("section#summary label"),
        function (element) {
          on_event(element, "click", function (e) {
            if (output_document.getElementById("results") === null) {
              e.preventDefault();
              return;
            }
            var result_class = element
              .querySelector("span[class]")
              .getAttribute("class");
            var style_element = output_document.querySelector(
              "style#hide-" + result_class
            );
            var input_element = element.querySelector("input");
            if (!style_element && !input_element.checked) {
              style_element = output_document.createElementNS(
                xhtml_ns,
                "style"
              );
              style_element.id = "hide-" + result_class;
              style_element.textContent =
                "table#results > tbody > tr.overall-" +
                result_class +
                "{display:none}";
              output_document.body.appendChild(style_element);
            } else if (style_element && input_element.checked) {
              style_element.parentNode.removeChild(style_element);
            }
          });
        }
      );

      function has_assertions() {
        for (var i = 0; i < tests.length; i++) {
          if (tests[i].properties.hasOwnProperty("assert")) {
            return true;
          }
        }
        return false;
      }

      function get_assertion(test) {
        if (test.properties.hasOwnProperty("assert")) {
          if (Array.isArray(test.properties.assert)) {
            return test.properties.assert.join(" ");
          }
          return test.properties.assert;
        }
        return "";
      }

      var asserts_run_by_test = new Map();
      asserts_run.forEach((assert) => {
        if (!asserts_run_by_test.has(assert.test)) {
          asserts_run_by_test.set(assert.test, []);
        }
        asserts_run_by_test.get(assert.test).push(assert);
      });

      function get_asserts_output(test) {
        const asserts_output = render([
          "details",
          {},
          ["summary", {}, "Asserts run"],
          ["table", {}, ""],
        ]);

        var asserts = asserts_run_by_test.get(test);
        if (!asserts) {
          asserts_output
            .querySelector("summary")
            .insertAdjacentText("afterend", "No asserts ran");
          return asserts_output;
        }

        const table = asserts_output.querySelector("table");
        for (const assert of asserts) {
          const status_class_name = status_class(
            Test.prototype.status_formats[assert.status]
          );
          var output_fn = "(" + assert.args.join(", ") + ")";
          if (assert.stack) {
            output_fn += "\n";
            output_fn += assert.stack
              .split("\n", 1)[0]
              .replace(/@?\w+:\/\/[^ "\/]+(?::\d+)?/g, " ");
          }
          table.appendChild(
            render([
              "tr",
              { class: "overall-" + status_class_name },
              [
                "td",
                { class: status_class_name },
                Test.prototype.status_formats[assert.status],
              ],
              [
                "td",
                {},
                ["pre", {}, ["strong", {}, assert.assert_name], output_fn],
              ],
            ])
          );
        }
        return asserts_output;
      }

      var assertions = has_assertions();
      const section = render([
        "section",
        {},
        ["h2", {}, "Details"],
        [
          "table",
          { id: "results", class: assertions ? "assertions" : "" },
          [
            "thead",
            {},
            [
              "tr",
              {},
              ["th", {}, "Result"],
              ["th", {}, "Test Name"],
              assertions ? ["th", {}, "Assertion"] : "",
              ["th", {}, "Message"],
            ],
          ],
          ["tbody", {}],
        ],
      ]);

      const tbody = section.querySelector("tbody");
      for (const test of tests) {
        const status = test.format_status();
        const status_class_name = status_class(status);
        tbody.appendChild(
          render([
            "tr",
            { class: "overall-" + status_class_name },
            ["td", { class: status_class_name }, status],
            ["td", {}, test.name],
            assertions ? ["td", {}, get_assertion(test)] : "",
            ["td", {}, test.message ?? "", ["pre", {}, test.stack ?? ""]],
          ])
        );
        if (!(test instanceof RemoteTest)) {
          tbody.lastChild.lastChild.appendChild(get_asserts_output(test));
        }
      }
      log.appendChild(section);
    };

    /*
     * Template code
     *
     * A template is just a JavaScript structure. An element is represented as:
     *
     * [tag_name, {attr_name:attr_value}, child1, child2]
     *
     * the children can either be strings (which act like text nodes), other templates or
     * functions (see below)
     *
     * A text node is represented as
     *
     * ["{text}", value]
     *
     * String values have a simple substitution syntax; ${foo} represents a variable foo.
     *
     * It is possible to embed logic in templates by using a function in a place where a
     * node would usually go. The function must either return part of a template or null.
     *
     * In cases where a set of nodes are required as output rather than a single node
     * with children it is possible to just use a list
     * [node1, node2, node3]
     *
     * Usage:
     *
     * render(template, substitutions) - take a template and an object mapping
     * variable names to parameters and return either a DOM node or a list of DOM nodes
     *
     * substitute(template, substitutions) - take a template and variable mapping object,
     * make the variable substitutions and return the substituted template
     *
     */

    function is_single_node(template) {
      return typeof template[0] === "string";
    }

    function substitute(template, substitutions) {
      if (typeof template === "function") {
        var replacement = template(substitutions);
        if (!replacement) {
          return null;
        }

        return substitute(replacement, substitutions);
      }

      if (is_single_node(template)) {
        return substitute_single(template, substitutions);
      }

      return filter(
        map(template, function (x) {
          return substitute(x, substitutions);
        }),
        function (x) {
          return x !== null;
        }
      );
    }

    function substitute_single(template, substitutions) {
      var substitution_re = /\$\{([^ }]*)\}/g;

      function do_substitution(input) {
        var components = input.split(substitution_re);
        var rv = [];
        for (var i = 0; i < components.length; i += 2) {
          rv.push(components[i]);
          if (components[i + 1]) {
            rv.push(String(substitutions[components[i + 1]]));
          }
        }
        return rv;
      }

      function substitute_attrs(attrs, rv) {
        rv[1] = {};
        for (var name in template[1]) {
          if (attrs.hasOwnProperty(name)) {
            var new_name = do_substitution(name).join("");
            var new_value = do_substitution(attrs[name]).join("");
            rv[1][new_name] = new_value;
          }
        }
      }

      function substitute_children(children, rv) {
        for (var i = 0; i < children.length; i++) {
          if (children[i] instanceof Object) {
            var replacement = substitute(children[i], substitutions);
            if (replacement !== null) {
              if (is_single_node(replacement)) {
                rv.push(replacement);
              } else {
                extend(rv, replacement);
              }
            }
          } else {
            extend(rv, do_substitution(String(children[i])));
          }
        }
        return rv;
      }

      var rv = [];
      rv.push(do_substitution(String(template[0])).join(""));

      if (template[0] === "{text}") {
        substitute_children(template.slice(1), rv);
      } else {
        substitute_attrs(template[1], rv);
        substitute_children(template.slice(2), rv);
      }

      return rv;
    }

    function make_dom_single(template, doc) {
      var output_document = doc || document;
      var element;
      if (template[0] === "{text}") {
        element = output_document.createTextNode("");
        for (var i = 1; i < template.length; i++) {
          element.data += template[i];
        }
      } else {
        element = output_document.createElementNS(xhtml_ns, template[0]);
        for (var name in template[1]) {
          if (template[1].hasOwnProperty(name)) {
            element.setAttribute(name, template[1][name]);
          }
        }
        for (var i = 2; i < template.length; i++) {
          if (template[i] instanceof Object) {
            var sub_element = make_dom(template[i]);
            element.appendChild(sub_element);
          } else {
            var text_node = output_document.createTextNode(template[i]);
            element.appendChild(text_node);
          }
        }
      }

      return element;
    }

    function make_dom(template, substitutions, output_document) {
      if (is_single_node(template)) {
        return make_dom_single(template, output_document);
      }

      return map(template, function (x) {
        return make_dom_single(x, output_document);
      });
    }

    function render(template, substitutions, output_document) {
      return make_dom(substitute(template, substitutions), output_document);
    }

    /*
     * Utility functions
     */
    function assert(
      expected_true,
      function_name,
      description,
      error,
      substitutions
    ) {
      if (expected_true !== true) {
        var msg = make_message(
          function_name,
          description,
          error,
          substitutions
        );
        throw new AssertionError(msg);
      }
    }

    /**
     * @class
     * Exception type that represents a failing assert.
     *
     * @param {string} message - Error message.
     */
    function AssertionError(message) {
      if (typeof message == "string") {
        message = sanitize_unpaired_surrogates(message);
      }
      this.message = message;
      this.stack = get_stack();
    }
    expose(AssertionError, "AssertionError");

    AssertionError.prototype = Object.create(Error.prototype);

    const get_stack = function () {
      var stack = new Error().stack;

      // 'Error.stack' is not supported in all browsers/versions
      if (!stack) {
        return "(Stack trace unavailable)";
      }

      var lines = stack.split("\n");

      // Create a pattern to match stack frames originating within testharness.js.  These include the
      // script URL, followed by the line/col (e.g., '/resources/testharness.js:120:21').
      // Escape the URL per http://stackoverflow.com/questions/3561493/is-there-a-regexp-escape-function-in-javascript
      // in case it contains RegExp characters.
      var script_url = get_script_url();
      var re_text = script_url
        ? script_url.replace(/[-\/\\^$*+?.()|[\]{}]/g, "\\$&")
        : "\\btestharness.js";
      var re = new RegExp(re_text + ":\\d+:\\d+");

      // Some browsers include a preamble that specifies the type of the error object.  Skip this by
      // advancing until we find the first stack frame originating from testharness.js.
      var i = 0;
      while (!re.test(lines[i]) && i < lines.length) {
        i++;
      }

      // Then skip the top frames originating from testharness.js to begin the stack at the test code.
      while (re.test(lines[i]) && i < lines.length) {
        i++;
      }

      // Paranoid check that we didn't skip all frames.  If so, return the original stack unmodified.
      if (i >= lines.length) {
        return stack;
      }

      return lines.slice(i).join("\n");
    };

    function OptionalFeatureUnsupportedError(message) {
      AssertionError.call(this, message);
    }
    OptionalFeatureUnsupportedError.prototype = Object.create(
      AssertionError.prototype
    );
    expose(OptionalFeatureUnsupportedError, "OptionalFeatureUnsupportedError");

    function make_message(function_name, description, error, substitutions) {
      for (var p in substitutions) {
        if (substitutions.hasOwnProperty(p)) {
          substitutions[p] = format_value(substitutions[p]);
        }
      }
      var node_form = substitute(
        ["{text}", "${function_name}: ${description}" + error],
        merge(
          {
            function_name: function_name,
            description: description ? description + " " : "",
          },
          substitutions
        )
      );
      return node_form.slice(1).join("");
    }

    function filter(array, callable, thisObj) {
      var rv = [];
      for (var i = 0; i < array.length; i++) {
        if (array.hasOwnProperty(i)) {
          var pass = callable.call(thisObj, array[i], i, array);
          if (pass) {
            rv.push(array[i]);
          }
        }
      }
      return rv;
    }

    function map(array, callable, thisObj) {
      var rv = [];
      rv.length = array.length;
      for (var i = 0; i < array.length; i++) {
        if (array.hasOwnProperty(i)) {
          rv[i] = callable.call(thisObj, array[i], i, array);
        }
      }
      return rv;
    }

    function extend(array, items) {
      Array.prototype.push.apply(array, items);
    }

    function forEach(array, callback, thisObj) {
      for (var i = 0; i < array.length; i++) {
        if (array.hasOwnProperty(i)) {
          callback.call(thisObj, array[i], i, array);
        }
      }
    }

    /**
     * Immediately invoke a "iteratee" function with a series of values in
     * parallel and invoke a final "done" function when all of the "iteratee"
     * invocations have signaled completion.
     *
     * If all callbacks complete synchronously (or if no callbacks are
     * specified), the ``done_callback`` will be invoked synchronously. It is the
     * responsibility of the caller to ensure asynchronicity in cases where
     * that is desired.
     *
     * @param {array} value Zero or more values to use in the invocation of
     *                      ``iter_callback``
     * @param {function} iter_callback A function that will be invoked
     *                                 once for each of the values min
     *                                 ``value``. Two arguments will
     *                                 be available in each
     *                                 invocation: the value from
     *                                 ``value`` and a function that
     *                                 must be invoked to signal
     *                                 completion
     * @param {function} done_callback A function that will be invoked after
     *                                 all operations initiated by the
     *                                 ``iter_callback`` function have signaled
     *                                 completion
     */
    function all_async(values, iter_callback, done_callback) {
      var remaining = values.length;

      if (remaining === 0) {
        done_callback();
      }

      forEach(values, function (element) {
        var invoked = false;
        var elDone = function () {
          if (invoked) {
            return;
          }

          invoked = true;
          remaining -= 1;

          if (remaining === 0) {
            done_callback();
          }
        };

        iter_callback(element, elDone);
      });
    }

    function merge(a, b) {
      var rv = {};
      var p;
      for (p in a) {
        rv[p] = a[p];
      }
      for (p in b) {
        rv[p] = b[p];
      }
      return rv;
    }

    function expose(object, name) {
      var components = name.split(".");
      var target = global_scope;
      for (var i = 0; i < components.length - 1; i++) {
        if (!(components[i] in target)) {
          target[components[i]] = {};
        }
        target = target[components[i]];
      }
      target[components[components.length - 1]] = object;
    }

    function is_same_origin(w) {
      try {
        "random_prop" in w;
        return true;
      } catch (e) {
        return false;
      }
    }

    /** Returns the 'src' URL of the first <script> tag in the page to include the file 'testharness.js'. */
    function get_script_url() {
      if (!("document" in global_scope)) {
        return undefined;
      }

      var scripts = document.getElementsByTagName("script");
      for (var i = 0; i < scripts.length; i++) {
        var src;
        if (scripts[i].src) {
          src = scripts[i].src;
        } else if (scripts[i].href) {
          //SVG case
          src = scripts[i].href.baseVal;
        }

        var matches = src && src.match(/^(.*\/|)testharness\.js$/);
        if (matches) {
          return src;
        }
      }
      return undefined;
    }

    /** Returns the <title> or filename or "Untitled" */
    function get_title() {
      if ("document" in global_scope) {
        //Don't use document.title to work around an Opera/Presto bug in XHTML documents
        var title = document.getElementsByTagName("title")[0];
        if (title && title.firstChild && title.firstChild.data) {
          return title.firstChild.data;
        }
      }
      if ("META_TITLE" in global_scope && META_TITLE) {
        return META_TITLE;
      }
      if ("location" in global_scope && "pathname" in location) {
        return location.pathname.substring(
          location.pathname.lastIndexOf("/") + 1,
          location.pathname.indexOf(".")
        );
      }
      return "Untitled";
    }

    /** Fetches a JSON resource and parses it */
    async function fetch_json(resource) {
      const response = await fetch(resource);
      return await response.json();
    }
    if (!global_scope.GLOBAL || !global_scope.GLOBAL.isShadowRealm()) {
      expose(fetch_json, "fetch_json");
    }

    /**
     * Setup globals
     */

    var tests = new Tests();

    if (global_scope.addEventListener) {
      var error_handler = function (error, message, stack) {
        var optional_unsupported =
          error instanceof OptionalFeatureUnsupportedError;
        if (tests.file_is_test) {
          var test = tests.tests[0];
          if (test.phase >= test.phases.HAS_RESULT) {
            return;
          }
          var status = optional_unsupported
            ? test.PRECONDITION_FAILED
            : test.FAIL;
          test.set_status(status, message, stack);
          test.phase = test.phases.HAS_RESULT;
        } else if (!tests.allow_uncaught_exception) {
          var status = optional_unsupported
            ? tests.status.PRECONDITION_FAILED
            : tests.status.ERROR;
          tests.status.status = status;
          tests.status.message = message;
          tests.status.stack = stack;
        }

        // Do not transition to the "complete" phase if the test has been
        // configured to allow uncaught exceptions. This gives the test an
        // opportunity to define subtests based on the exception reporting
        // behavior.
        if (!tests.allow_uncaught_exception) {
          done();
        }
      };

      addEventListener(
        "error",
        function (e) {
          var message = e.message;
          var stack;
          if (e.error && e.error.stack) {
            stack = e.error.stack;
          } else {
            stack = e.filename + ":" + e.lineno + ":" + e.colno;
          }
          error_handler(e.error, message, stack);
        },
        false
      );

      addEventListener(
        "unhandledrejection",
        function (e) {
          var message;
          if (e.reason && e.reason.message) {
            message = "Unhandled rejection: " + e.reason.message;
          } else {
            message = "Unhandled rejection";
          }
          var stack;
          if (e.reason && e.reason.stack) {
            stack = e.reason.stack;
          }
          error_handler(e.reason, message, stack);
        },
        false
      );
    }

    test_environment.on_tests_ready();

    /**
     * Stylesheet
     */
    var stylesheetContent =
      "\
html {\
    font-family:DejaVu Sans, Bitstream Vera Sans, Arial, Sans;\
}\
\
#log .warning,\
#log .warning a {\
  color: black;\
  background: yellow;\
}\
\
#log .error,\
#log .error a {\
  color: white;\
  background: red;\
}\
\
section#summary {\
    margin-bottom:1em;\
}\
\
table#results {\
    border-collapse:collapse;\
    table-layout:fixed;\
    width:100%;\
}\
\
table#results > thead > tr > th:first-child,\
table#results > tbody > tr > td:first-child {\
    width:8em;\
}\
\
table#results > thead > tr > th:last-child,\
table#results > thead > tr > td:last-child {\
    width:50%;\
}\
\
table#results.assertions > thead > tr > th:last-child,\
table#results.assertions > tbody > tr > td:last-child {\
    width:35%;\
}\
\
table#results > thead > > tr > th {\
    padding:0;\
    padding-bottom:0.5em;\
    border-bottom:medium solid black;\
}\
\
table#results > tbody > tr> td {\
    padding:1em;\
    padding-bottom:0.5em;\
    border-bottom:thin solid black;\
}\
\
.pass {\
    color:green;\
}\
\
.fail {\
    color:red;\
}\
\
tr.timeout {\
    color:red;\
}\
\
tr.notrun {\
    color:blue;\
}\
\
tr.optionalunsupported {\
    color:blue;\
}\
\
.ok {\
    color:green;\
}\
\
.error {\
    color:red;\
}\
\
.pass, .fail, .timeout, .notrun, .optionalunsupported .ok, .timeout, .error {\
    font-variant:small-caps;\
}\
\
table#results span {\
    display:block;\
}\
\
table#results span.expected {\
    font-family:DejaVu Sans Mono, Bitstream Vera Sans Mono, Monospace;\
    white-space:pre;\
}\
\
table#results span.actual {\
    font-family:DejaVu Sans Mono, Bitstream Vera Sans Mono, Monospace;\
    white-space:pre;\
}\
";
  })(self);
  // vim: set expandtab shiftwidth=4 tabstop=4:
}
